I live in Greenfield, which is right next to Squirrel Hill... and way cheaper to live in (although you'll be ecstatic about rents here pretty much anywhere). My bus ride to Oakland when I was in undergrad was about 20 minutes. Not too shabby, it was just incovenient to go home between classes. The bus runs pretty often between Oakland and Sq Hill as well. Shadyside is a nice part of town, even though I was mugged there once. It's a bit more expensive and pretentious, but very central to anything.
And of course you can find a very cheap place in south Oakland, but leave those places for the undergrads. Eccchhhhhh.