1. How early are you going to be? 4ish?
2. What do you mean by party? Isn't it just standing in a long line for a few hours waiting to buy a disc?
I'm thinking I'll get to one of my local stores around 5; I'm honestly not expecting that many people to be there. I'm just going for the experience, I should already have Leopard in my hands and installed on my Macbook by the time the stores open.
I've never been to one of the release parties, but the way I understand it, the stores make it to be a fairly big deal, and the Apple site calls it a world premiere party, hence my use of the word.