SUMMER SNEAKS : Drew, We HArdley Knew Ye : The littlest Barrymore finally seems back on track in solid film roles. Though she’s already lived several lives, her future looks bright. After all, she’s only 20.

One minute, a pixie-like Drew Barrymore is hunched over her iced tea at a sidewalk table at Pete’s Tavern. The next, her faded brown T-shirt is up around her ears.

The cherubic 7-year-old from “E.T.,” now 20, is flashing her unencumbered bosom to her lunch guest (in addition to restaurant patrons, pedestrians and motorists who happen to be passing). She’s demonstrating exactly how easy it was to bare her breasts for David Letterman on national television a few weeks back.

“It was definitely the most exhilarating minute of my life,” says Barrymore, who’s enjoyed more infamy than fame over her long and uneven acting career. Her bleached hair is slightly mussed, darker at the roots, and her face is makeup-free except for a layer of sickly chic brown lipstick. There is not one earring in any of the eight holes in her lobes. Plastic-tipped baby safety pins secure a pair of dime-store sunglasses.

“Any woman who tells me she sat next to Dave’s desk and didn’t want to get up and dance for him, they’re lying--or just really different than me and I can’t understand them,” says Barrymore, who has also been stripping recently at New York’s trendy Blue Angel club.

Letterman, who was legitimately surprised by the birthday present, may have put on his classic mock-shock expression for his fans, but he recently confided a slightly different take: “I guess an argument can be made that it was in bad taste, but I have to say from a professional standpoint and also from a personal standpoint, it was certainly one of the delights of my adult life.”

Besides, says her friend Nancy Juvonen, who makes up one-third of Barrymore’s year-old production company, Flower Films, “She’s really good at it.” This, apparently, is a compliment.

Barrymore’s pale, luminous skin doesn’t redden at today’s display. In fact, she hardly notices she’s given everyone on 18th Street a free show. “I’m so comfortable in my skin,” she coos, lighting a cigarette. “If you ever are lucky enough to get to that place in your life--and I had to go through tons and tons of (expletive) to get there--you have to take advantage of it. It’s not about exhibitionism. That’s where it goes wrong, when it becomes about wanting to show yourself, instead of just being able to.”

Now, with her performance as the boy-crazy and ultra-likable Holly in this year’s “Boys on the Side” under her belt, and her coming summer performances in “Mad Love” and “Batman Forever,” Barrymore has forced Hollywood to give her a second look--even when she’s fully clothed.

According to “Boys on the Side” director Herbert Ross, Barrymore rediscovered herself in the role of Holly.

“Drew recognized something in the role that hadn’t been tapped before. There was humor, wit and bravery--in addition to sweetness and goodness--all of which exist in Drew,” says Ross. “I had no idea she was an actress of the quality she is. I think this picture has done her a great deal of good. She’ll be taken seriously now.”

Her “Mad Love” and “Batman” co-star, Chris O’Donnell (whom she affectionately calls her “apple pie”), says Barrymore’s confidence surprised him. “Drew is not self-conscious at all. She’s very sure of herself--opinionated even,” he says. “She doesn’t sit and think about things, she knows what she likes and where she wants to go with her character. That makes her seem much older than she is.”

Barrymore’s mother, actress and recent sex-tips book author Ildiko Jaid Barrymore, says her daughter came into the world that way. “Drew was always very self-possessed,” says Barrymore. “She knew who she was and what she wanted in life--to a spooky level. At 4 she knew she wanted to be an actress. She was autonomous, independent, always focused on her goals and how to achieve them. Whatever I taught her by example was basically to allow herself the freedom to discover and the freedom to take risks.”

Juvonen describes her friend as “a cross between an 8-year-old boy and a 40-year-old woman,” who will wrestle and playfully “suck on” her buddy O’Donnell one minute and make cool-headed business decisions the next.

“Age has never had anything to do with it,” says Barrymore, her tweezed eyebrows giving off a look of surprise and disdain at once. “I learned that lesson really young, thank God. People who are wrapped up in age are closed off to a lot. It’s a very shallow way of thinking.”

Barrymore decided years ago that sex was the way to change her public image, which had gone from pigtails to party girl in no time. She started drinking at age 9 when her mother took her along to L.A. clubs and parties. She was smoking pot and snorting cocaine by 12, and at 14 she attempted suicide. Rehab soon followed, as did her tell-all book about her addictions, “Little Girl Lost.”

Though she finally sobered up, she was also washed up as she reached her early teens. No directors would give her a chance--until she snagged the role of a villainous teen-age sexpot in 1992’s campy “Poison Ivy.”

“I don’t give a (expletive) about sex appeal in my real life, but I knew I could work it for something,” she says, sounding more like the businesswoman behind her production company than the flighty flower child she’s playing this afternoon. “Everyone is fascinated with sexuality. I knew it was going to turn people’s heads.”

Besides, she had the tattoo described in the first pages of the script. “Excuse my dry scaly legs,” she says, rolling up her bell bottoms to reveal a cross covered in rose vines just above her ankle. This is only one of many such adornments, including a colorful butterfly below her exposed navel and two on her lower back.

It seems her plan has worked. Men on the street wave as they pass. College students surround her with scraps of paper to autograph. One young woman rushes to buy a disposable camera so she can pose with her favorite actress. “My roommates would never believe this unless I had it on film,” she says in amazement.

Barrymore prefers not to think about why people go out of their way to ooh and aah at her or why the waiters at Pete’s Tavern have on occasion had to make a human wall around her. “I have problems with it,” she says, rolling her eyes. “But I’m not going to try to understand why I’m being admired, because then I’ll just be an idiot.”

According to “Batman Forever” director Joel Schumacher, who has known Barrymore since she was 9 and later worked with her on the television pilot “2000 Malibu Road,” it’s her lack of inhibition in front of the camera that’s finally turning directors’ heads.

“I think Drew is one of the most honest actors I’ve ever worked with,” he says of Barrymore, whom he cast as Sugar, Tommy Lee Jones’ glitter-dipped girlfriend in the summer blockbuster. “With Drew, what you see is what you get. When the cameras are rolling, she starts speaking and you almost think she didn’t hear ‘action.’ It sounds like a conversation, not like acting.”

The camera--perhaps the only constant throughout Barrymore’s turbulent childhood--is more like a friend than an obstacle. She literally lights up when the lens finds her. During a photo shoot at Union Square while hugging a tree, she suddenly acquires The Look. Her eyes focus in on the camera and she smolders, transforming the drab grunge persona into a Lolita-esque starlet. ‘There is a luminous quality to Drew’s skin and eyes,” says Schumacher. “The camera just loves her and it has all her life--it’s a God-given gift.”

If you ask Barrymore about her talent, she’ll tell you she isn’t a good actress--or rather that good actresses don’t act, they become their characters. In “Mad Love,” which opens May 26, Barrymore is heartbreaking as Casey, a clinically depressed teen-ager experiencing love for the first time. “I thought of her as a beautiful flower that keeps trying to open up in the world,” says Barrymore, making a budding gesture with her hand, “but the world closes her up continually.”

She says she identified with the character, who attempts suicide throughout the movie.

“I know there aren’t many actresses in the world who’ve been institutionalized--gone through the (expletive) ringer and back out again,” says Barrymore of the time she spent in an institution for rehab. “I knew I could do this with my eyes closed.”

After one suicide attempt, as Casey lies restrained in a hospital bed, Barrymore’s misery is palpable. Her left hand, bound above her, tics with nervousness as tears leak from her eyes in shame and despair.

It felt so real, in fact, that Barrymore went to therapy for several months after finishing the film. “To be in that mentality constantly for three months--I must say it drove me nuts. It killed my spirit to play this character. But when it was over, the cathartic aspect of it kicked in and I felt freer than I’ve ever felt. To go through all that and come out the other side is a revelation in the highest sense--without question.”

Barrymore should know--she’s done it before. Drinking is a Barrymore family tradition as strong as the acting talents passed through the genes of her relatives, including her movie star grandfather John Barrymore (“Grand Hotel,” “Twentieth Century”) and her father, John Barrymore Jr., whose film career was cut short by a series of drug busts.

“I went through a very deep period of loneliness, just utter . . . from 6 to 16,” says Barrymore, somewhat tired of going over the territory. “I was drinking--yeah, but that’s like whatever, what-(expletive)-ever. What I have to say to the people who haven’t gone through a wild period is: Watch out, you know, it’s going to come in some way, shape or form. We all have to get that out of our systems.”

Schumacher says it worked. “I think she conquered many demons early in life and she’s come out the other end an extraordinary human being,” he says. “The nice thing about Drew is she’s gotten strong but not tough.”

In fact, there’s a new softness about the actress. It shows itself at the very mention of her boyfriend of one year, Eric Erlandson, 32. She met the blond guitarist for the band Hole while in Seattle filming “Mad Love.” She threw up on him one night at a concert--a true story--and the rest is history. “It’s really disgusting. I’m still in the throes of discovering my love,” she says, with teen-age breathiness. “It’s remarkable, I wake up every morning more in love than day before.”

Now the two live in Barrymore’s Melrose-area home in Los Angeles, which she had rented out for the past seven years. When the last tenants moved, the couple renovated the house top to bottom. They added a koi pond outside and moved in their three cats. Each of the house’s 10 rooms is decorated for different moods--a night sky in one, velvet couches in another. One room is reserved exclusively for Erlandson’s Buddhist prayers.

Three years ago Barrymore appeared nude in Interview magazine with then-fiancee Jamie Walters (who now plays Tori Spelling’s love interest on “Beverly Hills, 90210”), but even though she tattooed Jamie’s name on her lower back, the relationship didn’t last. Neither did the tattoo, which bled into itself recently, making the name undecipherable. Her marriage last year to L.A. bar owner Jeremy Thomas lasted less than two months.

“I’d marry Eric in a heartbeat,” she says dreamily and displaying a six-month anniversary ring--a plastic 70s-style butterfly ring, to match her tattoo and belt buckle. The ring also makes an appearance in “Mad Love.” Besides, a wedding would be for “the family.”

Since Barrymore is estranged from her father and has not had contact from her mother in recent years--though she says that relationship is thawing--”the family” would mean the Erlandsons, who live in Southern California. “I never thought I’d have a traditional family until I had one of my own--I know what all the fuss is about now,” she says of her beau’s large family, who treat her as one of their own. “Everything else dissolves around you and you’re lost in a really safe world.”

Being accepted by his family encouraged Barrymore to rekindle correspondence with her estranged mother, whose book, “Secrets of World Class Lovers,” is due this month from General Publishing Group Inc. Highlighted in the volume are pointers on “mastering oral sex” and “learning the finer points of body shaving.”

Jaid Barrymore, as she is now known, says she had nothing but pride as she watched her daughter take it off for Dave. “It would be disingenuous and hypocritical to disapprove of Drew after I posed for (the upcoming September ’95 issue of) Playboy,” she says. “She is an adult now. Who am I to shake a finger at her? I trust her boundaries and respect her choices. Besides, there was nothing sleazy about it. It was spontaneous, uncontrived and sweet.”

The mother, who lives in Los Angeles, and daughter have started writing letters. “It’s pretty thrilling any time I get a piece of correspondence from Drew. I just start crying. I’m like Niagara Falls. It’s the best thing,” she says, crediting the book with bringing the two together. “She has pride in me for having written this book that she never had before. There’s an ease and sweetness we never had.” As mother-daughter, the two could never get their roles right. So they’ve decided to start fresh--as friends.

“We’re discovering we really like each other,” says the younger Barrymore. “Love is almost easier than like. Love is like, I love him ,” she says, pointing to a man passing her table. Before bursting out into a peal of giggles, she yells a dramatic: “I love you!”

In fact, Barrymore says she’s never been so happy. But she’s also been in this business long enough to know nothing lasts forever.

“Life has waves in it,” she says, sounding suddenly older than her 20 years. “The truth is, no one’s going to want to ride the bad ones with you, but they’re always going to ride the good ones. It’s kind of sick, but that’s the way the world works, especially the Hollywood industry. If you don’t understand that, you’re in the wrong business.”