PuPo is an acronym of sorts that stands for "Pussy Potential". I.e. whether the party is worth coming to, are there girls there. Sometimes you're with a girl when you're on the phone and you can't say, "Tom, are there some sluts there that I can bang?" Instead you would use the term PuPo and Tom could instantly answer yes or no or perhaps go into detail if he feels the need. You typically would ask questions containing PuPo to make sure that the place you're going to isn't a sausage fest.
Tom: Dude, are you coming or what?
Joe: Fuck man I'm all the way down on Bluff, is the PuPo worth it?
Tom: Oh dude the PuPo is out of control. There are at least 30 girls here and only like 10 dudes. That skank Monique is giving everybody lapdances and Sherry has already sucked three cocks. Needless to say, the other girls are down too. There's PuPo here of epic proportions.
Joe: Shit man, you could have just said yes, I love pussy. I'll get in my car as shitfaced as I am and drive there.