Jen,

I'm pretty sure I just commented on another one of your posts, so hopefully this isn't too redundant! Again, though, I'd definitely start by running a search on iSport:

http://gymnastics.isport.com/gymnastics-gyms/?&l=&k=&ct=US

If you can't find any adult classes there, I'm a huge fan of contacting your city's Park and Recreation department. They generally have catalogs that offer a ton of different classes, many of which are geared towards adults.

Let me know if you still can't find anything after that. Hopefully it won't be that difficult, though!

Once you find a gym, try asking to have private lessons. There is a woman at my gym who comes for private lessons and she's getting pretty good!