5 miles round trip each day? You could purchase pretty much any bike and it'd work for you. Also considering the theft probability in SF, you'd probably be better off buying a $200 beater off of craigslist (or even a WalMart) bike.

That way when it gets stolen you're not out $700 and you probably wouldn't be on the bike long enough to use all of the bells and whistles on the more expensive bike.