I second Geo’s priceline suggestion. Mrs Kerr and I only live a 30 minute drive from Pittsburgh but often like to just stay downtown overnight after a game or a night on the South side, due to Mrs Kerr’s penchant for drinking too much beer and getting into fights (I’m only joking, and no, I’m not that dentist. We both do like a drink though).
We’ve stayed in the William Penn for prices that would make a Super 8 go out of business; it is highly demand based though, I wouldn’t try it the weekend of a Steelers home game or this weekend say with the Flyers in town. Pirates home games don’t seem to affect it much though (I wonder why….).
The only one to be slightly leery of is the Marriott; fine hotel but it’s right next to the igloo at the wrong end of downtown for the Pirates. Still walkable but a little further than any of the others. Nearer the original Primanti’s in the strip district though.