Hi buddy! Let's see how I can help you out here. You've got an interesting situation on your hands, essentially being a US citizen who grew up in China. In essence, you're applying from the same perspective as a Chinese citizen. Your scores aren't too bad, although retaking the GMAT just to shoot for a 730+ would REALLY help your chances. Your US volunteer experience will help put some of the "culture clash" worries at ease, so let's look at some programs. I'd suggest looking into Texas A&M, UW - Madison, Michigan State, and UIUC, all fantastic programs. Hope this helps you out, and let us know if you have any more questions!