The good news: Starting May 16, travelers will be able to fly nonstop from San Diego to Honolulu without connecting through Los Angeles (as now required). The bad news: There will be only two flights each week. The Boeing 757 service, on Saturdays and Sundays, will be provided by Pleasant Holidays via American Trans Air, which Pleasant Hawaiian normally uses for its package tours. However, the air fare, starting at $366.12 round trip, including taxes, can be bought on its own. Reservations: (800) 242-9244. . . . Nearly 30 million people visited Smithsonian Institution museums and the National Zoo in Washington, D.C., last year, a whopping 22% increase over 1996, the Smithsonian reported.