<p>Sounds cool. I'm also applying to some summer programs, so I didn't want to apply so early, and reject their offers, which would be rude. When did you ask?</p>
<p>Hmm... mine was during the school year and I didn't have alternate plans. However, when people replied after I had accepted one professor's offer, I wrote back "Thanks so much for the offer, but I was fortunate enough to have been accepted by _____ and will be working with him"... so it's not too hard to turn down offers graciously. </p>
<p>You should find out when you'll hear back from your summer programs and, if it's not too late, plan to send out e-mails right after you hear back. Or if you'd rather ask them early, you could write something like, "I am considering... blahblahblah" instead of "I AM GOING TO DO THIS."</p>