Yes - but we are in region 5 and do USTA and the occasional AAU meet. My dd competes sub-novice tumbling, but no tramp or DM - as our club doesn't offer either (and that DM scares the crap out of me!)
My dd also LOVES tumbling, though she is more concentrated toward artistic gymnastics. I really love USTA & AAU as it has allowed for my dd to be active in the meet scene while not being old enough to do sanctioned competitions through USAG. I think it's been a great experience for her. She is comfortable in front of the judges and with a large audience - which I think is great. Depending on the size of the meet, there can be tons of people at these tumbling meets, and sometimes the venue is quite large. The tumbling scene has really given her a chance to get used to that type of situation, so rather than focusing on the fact that there are a billion people in the stands, she can focus on her passes. And as far as that goes, I think it will be easier for her to adjust once she gets more into the gymnastics scene.