How can I find a good art class in San Francisco?

I asked this question a while ago but at the time no one was able to help – I’m hoping maybe new fluther users will have an answer. I’d like to take a watercolor painting class in SF, but I work full time and only have time to take a class that meets one night a week. City College offers a class that sounds great and is affordable, but it’s two nights (6 hours) a week. Any other ideas for classes?? I’d be willing to go to the east bay too, but I don’t have a car, so it has to be near BART.