San Francisco isn't the only California city with a transportation system that draws tourists - not since last July, when San Diego inaugurated its fire-engine-red trolley service. With an almost fire-engine-like speed - on an average under 40 minutes - it covers the 16-mile stretch of track from downtown to the Mexican border, carrying from 12,000 to 18,000 riders daily.
Of course, not all of them are tourists. San Diego's trolley is part of the city's regular public-transport network, and it's used by a great many commuters to the Navy yards, for instance, and to get from some of the bedroom suburbs into town. But since it began operation it also has drawn riders who want to add the fun of trolley riding to their San Diego visit, or who want an easy and convenient way to get to one of the city's major tourist attractions: Tijuana, just across the border in Baja California.
''I rode it,'' an enthusiastic friend said recently. ''I've lived in southern California all my life and have never even ridden a bus before. When I saw it, I knew I had to have a ride! It wasn't clanky or strident; it was cheap; and, in the long run, it was easier than crossing the border in my car.''
To cross the border in your own car may seem the easiest way to go, but it often entails a long, drawn-out customs search upon your return. In addition, few drivers would do it without an extra and sometimes costly insurance policy.
Another way to cross the border is via Mexicoach, a bus service that leaves San Diego's Santa Fe depot about every two hours and goes nonstop through San Ysidro to a terminal about a block from Tijuana's shopping district. The cost is customs checks - longer coming back.