Change of Plans

A couple of days ago I booked my flight to Phoenix as part of my summer vacation to hike to the Grand Canyon. My friends were taking an extended road out there and I was going to meet up with them so we could camp at the bottom. However, today I was informed that one of the drivers had backed out so the trip is in jeopardy. My flight is non-refundable so no matter what I'm going to the southwest. Where should I go? What should I do? I know next to nothing about the area. I've got an uncle who lives who there along with a couple of cousins but I don't want to impose them so I've got to find my own entertainment. San Diego and Los Angeles are less than six hours away if all else fails.