If you can get into one and have the time, a regular summer program would be best. You'd be with younger girls mostly, but if it's OK with the school, you should do it. They typically last about 5-8 weeks. That's enough time to make a LOT of improvement.
There is also an "adult dance camp" in Richmod, VA. It's only 1 week long, but if that's all the time you have, it could be worthwhile.[/i]