The impromptu car show, as you call it, will be maximum on Saturday night, and Friday will probably have a good turnout, too. It's mostly the hot rodders and rat rod folks -- and lots of racers walking around and looking at all the stuff on display. Parking your street vehicle will be dang near impossible right there -- in the lots at the Stateline (or whatever that casino is called), so plan on walking at least from the lot across the street at the Montego Bay. We stay at the Quality Inn and walk the couple of blocks to the "show".
The busiest times at the show are after dark, so if you're shooting photos -- either have the camera set for high ISO or have your flask with you. And the sow is where there's usually at least one guy with a gas-powered drink blender making margaritas for donations or five bucks or something. I don't know if his blender is like the one the Bean Bandits used to run (I think it was them - someone correct me if I'm wrong). Theirs ran on nitro. Interest use of "spare" fuel. . .