You all should definitely check out Baileys. I'm not good at crowd estimates, but there are well over 100 Steelers fans there for a big game.
Baileys is in Ballston Mall and I think it used to be a JC Penney's. That will give you an idea of the size. The bar is divided into three main rooms. All the games will be on, but there will be one "featured" game in each of the room.
There will be a lot of Redskins fans but there are often just as many Steelers and Eagles fans. Giants are probably a fourth and then Pats.
Anyway, like most of you, I have NFL Sunday Ticket so I don't go as much as I used to but for those times when you can't see a game in person and want to be around a bunch of screaming fans, Baileys is a great choice. I took my parents there (my Dad is from Connellsville) for the first Bengals game last year and the game was on the main room. We had a great time in spite of the way things turned out.
I also hear Southside 815 is a Steelers bar but that place isn't very big.