Oh my, there are so many options. And it depends on your budget. Herbivore (one on Valencia and one on Divisadero) and Cha-Ya (also on Valencia) are the two kind of middle price range spots that come to mind. Both are really good! And if you're in for an expensive vegan-meal-of-a-lifetime kind of experience, Millennium (on Geary at Jones) might be the best gourmet vegan food anywhere. For low-budget, there are lots of taquerias that have vegan options. Other people might know more about strictly vegan low-budget options though. We don't live in the city, so we tend to eat out at the more special occasion places when we're there. Have fun!