I probably won't make the meet, but there is an SCCA autocross the following day (Sunday 4/1/2012) at Gateway International Raceway which is now called Gateway Motorsports Park in Madison, IL right across the river from St. Louis.
If anyone comes in from out of town, this would be a great way to make a weekend out of the trip.
Show up at around 7:00-8:00am and sign up, it'll be a fun day. I'll be there with my E90 M3. You can expect at least 4 runs at an STL event, sometimes more depending on turnout. The cost last year was $35 I believe but 2012 event fees haven't been posted yet.
If anyone is interested please feel free to contact me and/or check out
http://www.stlsolo.org for event details as we get closer to the event.
Most people's cars on the forums probably slot nicely into the STU class which is a class for street-tired high-hp cars with basic performance and cosmetic modifications like suspension, wheels, brakes, exhaust, engine tunes, etc.