Heh, beer pong. I live a few blocks from a university and it's pretty much the official sport of my neighborhood, that and screaming Neil Diamond songs as you stumble down the street at 2AM RIGHT OUTSIDE MY FREAKING WINDOW ARGH. I have never played it, though I have been in places where it was going on several times. The nice thing about a party is, there are usually a wide assortment of people there, and chances are, everybody there isn't there just to get drunk.
I understand ya though, I have periods sometimes where going out anywhere is a struggle. Sometimes I do stay in when my friends are going out, and sometimes you REALLY need that quiet time or else things can get ugly. I guess I'd say that if you do end up going, really try not to worry about whether or not you're being "sub-par". People probably like your true personality more than you think they do. And don't feel like you have to stay the whole time, either, CanadianRose's post is right on.