At my interviews they seemed to stress that if you have other deadlines with other schools, or any reason that you can't give an answer within their allotted time, let them know and they could possibly work with you. I was accepted at my 2nd choice before my 1st. I called my #1 and let them know that I had a deadline to meet but they were still my first choice, asked what information they could give me at that time. They were able to give me a decision within the time frame required. I would definitely at least ask the first school if they would be willing to extend the deadline for you in the event that you are unable to make a decision (probably unlikely, but possible), and let your top choice school know that you have a deadline and if there's any info they could give you to help in the decision (maybe where you stand on a waitlist, for example). Letting them know they are your top choice may even help you. I would imagine most schools want to accept students that want to be there.

I would imagine most of the schools are somewhere between 10 and 30 days. If they require acceptance before you find out from your other school, you could always just accept the offer. Then if your first choice school accepts you later, call the school you were previously accepted at and let them know of the situation.

In that situation you would lose whatever money you had to pay with the deposit they require, which is no small chunk of change. But in the end you have to chose what is best for you and your situation. If you chose to go this route though I would encourage you to be as professional as you can and notify the appropriate people as early as possible so that they can find someone to fill your spot.

I hope that helps, but its kind of a sticky situation.