Surfing in the Bay Area is hard for a number of reasons: you need a car and a surfboard, the water is freezing cold (you need a thick wetsuit), Silicon Valley is inland and blocked off from the ocean by a mountain range, and the good waves are mostly for experts. That said, Cowell's in Santa Cruz is probably one of the best places in America outside of Hawaii for a beginner to learn. You can get there with a combination of train and bus and then rent a longboard for an afternoon. Pacifica isn't too bad for a beginner, either... but you'll need your own gear and a car.