Soma or North Beach
slpsys: In my humble opinion, it doesn't matter so much where you sleep as much as where you hang out/hack/work (you are an entrepreneur, yes? why are you sleeping?). I presently live in NOPA, and for me, it's easier to find cheap housing, and a quick bike ride or bus ride on the 5 to (or 24) to downtown (SOMA'd be a few more blocks' walk).natemartin's right, though; north beach probably wouldn't be the best fit.