I'm leaving in two weeks for the summer, should I tell the guy I like him now or wait till I get back?

Ive started to like a freind, and I think he may like me as well. The thing is in two weeks I am leaving town and wont be back until the end of summer. Would it be better to wait until I get back to ask if hes interested or should I do that before I leave? I will be gone for two months, and if so how should I go about informing him I like him?