Disney Channel does do open talent calls in the Summer. They usually do 2 open casting calls every summer, of course the 2012 one has already passed.
You could wait until the 2013 one. BUT, I am going to be honest. I went to the 2011 Disney Casting call they held in Austin, TX. And, it was horrible. They make you go audition in a group and trust me, they won't even give you a glance unless you seriously put yourself out there, which you don't even have time to do. They give the group less than 10 minutes and then it is over. I would suggest getting a talent agent, and just going through the agency.