First, remember that SF is a relatively small city, and you can get from pretty much anywhere to anywhere else in the city via public transit in about an hour max. So don't immediately discount all the areas that don't have startups. There are plenty of other areas in the city that get you more apartment for your money, and more diversity in the people around you (diversity as in not just tech workers)

That being said, if you really want to live where you work, probably go for SOMA. Most of SF's startups are clustered there. Be ready for high rents though. And talk to someone who's lived there for a bit to find out which areas of SOMA you'd want to live in, and which you don't. (Actually, I can help you with that if you want!)

North Beach has some good bars, lots of good restaurants, lots of crappy clubs, and tons of d-bags. Not many startups that I know of. Nice to visit friday nights, I wouldn't want to live there.