Foo Fighters gen. admission ticket question?

I have general admission tickets to the foo fighters at the peterson events center in pittsburgh this summer. first..what time should i get there to get in line for a good standing place? My fiance goes to metal/hard rock concerts a lot and says that we don't have to go really early because he can get us up front, but i have a feeling the foo fighters will be harder to get close. This place looks smaller than most venues i've been to. And also...so if you have gen. admission tickets and you have to pee like halfway through the opening acts are you screwed? lol thanks in adance