"Don't be afraid of the big ones," said the 40-year-old mother of two, shoulders thrust back, head as high as she could manage on a 5-foot frame.
Her sisters, Francisca, 34, and Elda, 30, walked with her.
"Be like the men -- aggressive," Elda called out. During the week, the sisters spend their days like scores of other illegal immigrant women in Los Angeles: Wedged behind Singer sewing machines, they feed pants and shirts under the needle until their shoulders grow stiff.
But on the weekends they play a game that was off-limits to them in Guatemala. It is on the soccer fields that the Lopez sisters feel like American women.
Growing up at the foot of the Sierra Madre in northwest Guatemala, the Lopezes didn't need to be told that soccer was forbidden. Women did not wear shorts. They did not play games that required machismo.
"The indigenous people didn't like women to play," Celestina said while making tamales for dinner at her Westlake apartment one Thursday after practice. "There were evangelicals who didn't like it either."
There were six children in the Lopez family, three boys and three girls. The oldest, Juan, made the family's first soccer ball out of spare fabric when Celestina was small. She and her sisters were not allowed to play with it.
Her father, Francisco, an evangelical Christian, was a cattle and sheep farmer. He frowned on women playing rough sports like soccer but shared his countrymen's passion for the game. He attended the town's Sunday soccer matches and sold ice cream to spectators. He went to see the popular local soccer team, Club Deportivo Xelaju Mario Camposeco, "Los Superchivos," in nearby Quetzaltenango, where they filled the 13,500-seat stadium. He even took a few of his children to the game, including Francisca.
At night, Celestina would hear her brothers and other neighborhood boys calling to one another to play soccer.
She and her sisters would join them on the dirt roads, under the apricot, plum and palm trees. But the girls would never play.
"We would go and watch, only watch," Elda said.
On Jan. 20, 1994, Celestina left her small town of San Carlos Sija for the U.S., following the path of relatives. With no legal papers, she traveled by land, paying a coyote in Tijuana 15,000 quetzals, about $2,000, to guide her into California. It took her two tries to make it to Los Angeles.
Francisca followed the next year -- after five attempts over a dangerous route across the desert into Arizona. Elda arrived in 1996, again with the help of a coyote.
Life in L.A. proved harder than the sisters had imagined. The only jobs they could find were in garment factories, piecework that paid less than minimum wage with no benefits.
But they began building lives much as they would have in Guatemala: marrying, having children and joining an evangelical church, the Centro Cristiano Vida Victoriosa in Echo Park.
It would be years before they started playing soccer, almost by accident.
In the spring of 2006, after more than a decade of living in Los Angeles, Celestina heard an announcement at church: The minister was organizing a women's soccer league.
The sisters borrowed shin guards from their husbands. They bought knockoff Adidas cleats for $25, almost a day's pay, at Pepe's Sports near MacArthur Park because they knew the owner, a fellow Guatemalan. They persuaded their husbands to watch their five children.
Celestina had already practiced with her husband, Raymundo Hernandez, 35, who had played soccer in Guatemala since he was a child. But she felt awkward in the new cleats, "like a cow in shoes."
She and her sisters were nervous and scared to play. None of them had medical insurance in case they were injured.
But that was not their main concern. Their husbands had played without medical insurance for years and had never been hurt.
The sisters' biggest worry was that they might embarrass themselves by making stupid mistakes.
But as they played that first day at Belmont High School, and in the weeks that followed, Celestina grew confident. Not only could she and her sisters play, they looked forward to it. It loosened them up, relieved the stiffness in their shoulders.
Celestina and Elda felt less stressed. Francisca felt less depressed, stopped having headaches and breathing problems.
After about a year, the women's soccer games became so popular that the minister decided they were distracting churchgoers and discontinued them.
Celestina was secretly pleased. Playing under the minister's watchful eye, she felt she had to be on her best behavior. They would start their own team. For help, they turned to another Guatemalan immigrant.
On any given weekend, scores of immigrants line the hills of the bowl-shaped field where Celestina and her sisters play in MacArthur Park. Vendors with strollers full of Gatorade and Cheetos compete for territory closest to the field, bickering in Spanish. Men stand in clusters on the sidelines, following the action. Mothers dressed in heels and glitter-dusted jeans watch with babies hoisted on their hips. Boys and girls roam nearby, passing soccer balls.
Daniel Morales started the league, Youth Empowerment Through Scholastic Sports Service, for low-income, mostly immigrant children seven years ago. It has grown to about 1,200 players, including a dozen women's teams he refers to as "the ladies."
Annual dues are about $12. Games are usually on Saturdays, with optional practices during the week, and a season that effectively runs all year. Uniformed referees have whistles and carry penalty cards in their pockets, but in some ways the league is still informal.
The medic is an elderly Mexican cowboy who watches games from a folding chair on the sidelines. At the end of the winter and summer seasons, everyone receives a trophy.
Francisca remembers how giddy she felt the day she picked up her first uniform for $25, packaged in crinkling cellophane, like a toy.
"I wasn't a woman," she said, "I was a girl."
Celestina and her sisters didn't have to recruit much for their new team.
Women started approaching them in the park. Eventually, they attracted about 10 regular players, mostly fellow Guatemalan immigrants who had always wanted to play and finally felt free of family constraints.
"Here, you have the freedom to play for yourself," said Francisca, who plays offense. "There, if your mother or father-in-law says no, you can't."
Celestina and her team faced resistance.
Drunks shouted directions from the sidelines. Strange men in cowboy hats and paint-spattered pants gathered on the sidelines during games to stare at their bare legs.
"I can see how they look at us," Celestina said, "Like, who are these people and why are they playing?"
Back in Guatemala, attitudes about women's soccer are entrenched. Even members of the national women's team have fought with their families for the right to play.
When the sisters recount games to immigrant co-workers at the garment factories, some are shocked.
"Do your husbands know you play?" one woman asked Francisca.
"Did they allow you?"
Some Guatemalan women are afraid to play. Last month, the sisters tried to persuade their cousin who had just arrived from Guatemala to join the soccer team. She refused, afraid to wear shorts.
"Everyone will look at my legs!" she told Celestina.
Their mother, Catalina Velasquez, 75, did not find out they were playing until last month, and only by chance.
The sisters had not told her about their team because, like their father who died seven years ago, they thought she would disapprove.
But one day last month, as Elda was talking to her mother on a pay phone, she let the news slip.
"I have to go because I have a game," Elda said.
Her mother was shocked.
"What game?" she said.
Their time on the pay phone was about to run out.
"Fútbol," Elda said.
"Soccer? What? What are you talking about?" her mother said.
Elda had just enough time to reassure her mother that all three sisters play together, under the watchful eye of Celestina's husband, Raymundo Hernandez, who coaches the team.
A month later, their mother is resigned to the idea of her daughters playing soccer, they said. But she is not happy about it. She is convinced someone else must have given them the idea.
"Now," Raymundo said, smiling, "she is mad at me."
Thursday nights, the Lopez sisters and half a dozen teammates meet for practice in LaFayette Park.
Raymundo, 35, also a garment worker, is a demanding coach, pushing them to run faster, pass deliberately and charge the ball. Soccer has proved a common passion for him and Celestina. The game has been a way to escape from the cramped two-bedroom apartment they and their two children share with his sister and her two children.
During practice, Celestina and her sisters sprint, pass and scrimmage with teammates between fluorescent plastic cones on a field worn to dirt. Trash cans and palm trees serve as goals. When the light fades, they play by streetlight.
The sisters' five children play nearby. Celestina has been encouraging the only girl, her daughter, Erica Hernandez, 8, to play soccer, too, but she is scared of getting hurt.
The women practice surrounded by male soccer players engrossed in their own games, in the shadow of the park's official field.
The oasis of fenced artificial turf and metal goals glows under high-powered lights, and is always reserved by men's teams. Latina onlookers of all ages ring the field until well after dark, some still in work uniforms.
Celestina and her sisters dream of one day becoming the champions of MacArthur Park.
The sisters say their biggest challenge will be age and inexperience. They already think they run too slowly, pass too awkwardly and score too little, occasionally knocking the ball into their own goal. They are disappointed with their record this spring -- one win, one loss, five ties.
Each game, they play hard -- heading the ball, tumbling to make a save, rushing their opponents' goal and shouting at each other to score.
"We are not tall," Francisca says, "But we are not scared."