Vacation Ideas?

I need to come up with a summer vacation destination ASAP so PLEASE help me.

My main requirement is that it not be too hot/humid in July which knocks out Boston, Charleston, New Orleans, Savannah, Arizona etc. Requirement number two is that it not be too very far away because I don't want to waste all my time traveling. That knocks out Japan and Australia. Marcus insists that it be somewhere safe and modernized so Russia and Peru are out of the question (although I would love to see Machu Picchu some day).

I'm not a huge fan of hanging out on beaches, but I do like to snorkel so Hawaii is one idea. We just took a cruise in the Caribbean a few months ago though. My ideal vacation spot is somewhere that's beautiful, not too very crowded or expensive, and has some historic, geological, architectural, or cultural sites to visit. Any ideas??