A nearby town has a nice bmx track. I covers maybe an acre and a half, it's full of bumps, banked curves, etc. Neally nice. The rules say no kickstands, no reflectors, no chain guards. You must wear long sleeves and long pants. They say nothing about bmx or mtb. It has lights, grandstands, etc. Think I can ride my mtb there?

You should be able to. Sometimes jumps configured for small wheels are a bit lippy and odd for the big wheels but that's usually more to the DJing end. BMX race tracks are fine and, in fact, many race promoters offer 4-cross racing on their BMX tracks (there's one in Port Orchard, WA that does indoor 4-cross during the winter). Rip it up and have some fun.

It's not uncommon for MTBs to run in cruiser class, in BMX races.