Donnie is great but don't buy the first thing you like. Chat to the breeders, get a feel for whether you trust them, take your phone so you can do a bit of instant research and avoid the half dead limp looking creatures of which there are unfortunately a few!
If there's anything that catches your eye before you go drop me a pm as I know a few breeders who are going and who I'd recommend and I may know someone working with the species your looking at.
That said if you're simply going on spec then the September one may be better. A number of breeders I've been speaking to have said breeding has been much later this year and they may not have animals ready that they intended to so stock may be down on what it usually is.
I'm going anyway because a) its only 40 mind away for me and b) I have some snakes on hold that I'm picking up