I have many fond memories of making the two hour drive down to the AstroHall for the HGCA shows.
They were huge affairs, and had a number of repeat vendors of good character and quality.
The Joe's Crab Shack was one of the better ones in the Harris Co area, too.
Bellaire was not a bad side of town (other than the having to drive past Galleria and all that stupefied traffic) to get there. No where near as sketchy as going to George R Brown there at the intersection of the 4th & 5th Wards. (GRB shows were no ammo and zip tie everything, and that was before LTC, so extra sketchy as it got dark.)
I know that I learned, quickly, that the best method was to walk all the way to the back, and work forward, so you did not have to leg it through the entire show to leave.
Mind, that was back in the days when there would be 4-6 guys with nothing but milsurp parts to pick over, too. And some real militaria vendors as well. Only place I've ever seen an M-8 Carbine grenade launcher for sale , too (stupidly left that on the table for being $200).
When they moved to NRG Hall, they were laid out in an "L" which made for an annoying route to try and walk. There was no rhyme nor reason to the vendors, the HGCA members were not all piled up at the "'front" of the show; the traveling vendors were not at the "back," so it was utterly disorganized. Those shows also seemed to be about 75% of the AstroHall shows, and that only decreased over the years.
I'm glad I never had to pay for parking, because that would have been a bummer.