Solid advice right here. I looked at the guy I wanted to buy from... he didn't have a website, but there were some reviews on forums about him and things he has sold in the past. Everything looked good, so I went for it, and was extremely happy. I'm not sure if he'll be at that show or not, but it's Rick Krumrine. He keeps a lot of different snakes. Good guy and was great at following up with me afterwards.
I will say, that unless I'd buy from him again, I likely won't buy at an expo. Honestly, there are plenty of good breeders here on this forum who likely have (or know where to find) what you want. Their prices are good, and I have yet to see any sellers here that wouldn't back up what they are selling. I know expos and shows in other places have a lot of top-notch vendors, but the ones here near Pittsburgh, Pa made me feel questionable...