I haven't been to a repticon yet. I've noticed that they are expanding their venues greatly, so greatly that there's sort of a ridiculous (in my opinion) situation in the northeast: White Plains show (not Repticon) 1/23 which is a big NY city area show, Repticon 2/11-13 in Edison NJ, Repticon near Philly 2/25-27. That's 3 shows in about 5 weeks. Especially since the Repticons are now combining with the SuperPet expos, I'm not expecting much (the vending fee was also pretty high). I'll be in Philly on 2/25 so I'll probably check it out.
As far as what to look for at a reptile show and what to avoid, when looking for a leopard gecko I would avoid the following:
-vendors who have many different species including a leopard gecko or two. It's likely that they've acquired the leos from somewhere and are moving them along and that they don't know much about them.
-tables that have a whole bunch of tiny leopard geckos for $10 each. You get what you pay for.
I'd recommend, if possible, finding someone where the geckos are at least 15 grams or so (you can ask what they weigh and the person should know,or be able to give a good estimate), preferably where leopard geckos are nearly the only species sold and where the vendor knows the genetics of what s/he's selling.
Good luck,
ALiza