craftgrrl | SF bay area - best fabric stores?

I'm not sure how many of you are in the bay area, but I figured this was worth asking. I'm having a pirate-theme party pretty soon, and have been thinking about trying to sew something for my costume. My last experience at the local JoAnn's left something to be desired, so I was wondering if anyone here might have better suggestions.

I live in Redwood City, would prefer somewhere on the penninsula, but anywhere from San Francisco to San Jose is fine. I'm looking for decent prices and a really wide variety of cheaper fabrics that would work well for costumes and basic skirts, cotton or blends. Thanks!