Thanks for the advice guys. I ended up taking light rail from Timonium - although the train service was out of order and they used buses to bring us in. Can't beat a round-trip ticket for only $3.50.
Although, again, it baffles me how cities like Baltimore and Pittsburgh build stadiums with parking lots that are all reserved pass for season tickets holders only. How can there be no parking for out-of-town visitors? When I go to Philadelphia or Giants Stadium to catch a game, there's plenty of parking everywhere!