Another option to throw out there - Steel City!
It's the "championship" race and some pretty exciting racing happens there. Two years ago - Pastrana and Roncada battled down to the last moto for the 125 crown. Last year, RC dropped down to the 125 class and the Brown/Langston battle was one the the best races I had ever witnesses (right up there with the '02 Pontiac SX). I mean after moto 1 - it looked like Brown's chances were shot. Then second moto watching Langston's wheel come apart was amazing. And seeing the emotions after the race and everything. Brown let Jesseman go past him to give RC the win to go down in the 125 record books. What a race!!!
The track is a good spectator's track - perhaps better than Red Bud. At Red Bud - you have to see the track in sections, no easy way to see it all. At Steel City, you can see pretty much the whole thing from several spots. Lots of jumps but nothing monsterous like Larocco's Leap. There is amatuer racing all weekend on the Pro track, too (Friday and Saturday). [Red Bud has amatuer racing on Friday and Saturday nights on a SX-style track - and a cool 4th of July fireworks display Saturday night] FMX'er Mike Jones lives on the property at Steel City, too, and last year on Saturday afternoon - he, Trevor Vines, and Dan Pastor put on a really cool freestyle show at Jones' house (if you're into that kind of thing). Plus the race is on Labor Day Weekend so you have one day less of vacation to take. Pittsburg is 30-40 miles away.