I think I can help... DOn't hate, but I coach a High School pom squad, and we do the UDA competition every year at DHS. It is typically the first weekend in Feb, actually Wed. - Sat. We always stay at All Stars, but we also have the otpion of CBR if we want to spend more. UCA (cheer) has their competition in Jan.
The competitons take place in the Indiana Jones theater, and the girls overwhelming prefer DHS to the other parks for the thrill rides. That said, they have very little free time between practice and competition. So, you will see some HS aged girls, many in costume, and they will be giggling and acting like they do. But it really does not have an impact on the parks, I promise. There just aren't enough of them to make a huge impression on crowd levels. HOWEVER, I would not stay at ASMu or ASSp during these times. We use the aprking lots to practince late into the night (sorry!) and try as I we do to get the girls in bed and quiet, you know how that goes. So, if you stay somehwhere else, my guess is you won't be affected at all. You can always go on the UDA and UCA websites to find out when the competitions take place.
Have fun!