As Greg said, most of the Colorado "Must Do’s" will still be unridable well into June.
As for Rideables, I second your choice of Fruita and Greg’s recommendations of Buffalo Creek.
If you’re going to Fruita and want to do serious enduro, be sure to hit the Lunch Loops outside Grand Junction.
Here’s other Colorado classics that are clear now or should be clear by then:
Phil’s World
http://www.singletracks.com/bike-trails … world.html
Telegraph Trails
http://www.singletracks.com/bike-trails … gulch.html
Hartman Rocks
http://www.singletracks.com/bike-trails … rocks.html
The Boneyard and/or Wordl’s Greatest
http://www.singletracks.com/bike-trails … atest.html
If you’re planning to go through Colorado Springs, PM me and maybe I can break away to show you some of our great enduro routes.