Within my experience, i would absolutely 110% recommend that you choose the Winter Park/Frasier Valley out here in CO, or Moab, or BOTH.
Winter Park/Frasier Valley: Winter Park is IMO, the best bike park in the lower 48, perhaps only eclipsed by whistler, which happens to be owned, built and maintained by the same people. I would recommend WP over Whistler due to cost savings, easier travel (easy road trip from chicago), and less crowds. Unless you really want gnar gnar, you'll have trouble finding WP lacking. (if you do want gnar, you also have Keystone and Sol Vista nearby) on top of the bike park, you have literally thousands of miles of trails branching out through the Frasier Valley, into the high country of the rockies, and beyond. I've never done it, but i know i could ride from home in Louisville (near boulder), to Winter Park, and beyond, only requiring crossing pavement, not ridding on it. The combination of the Trestle Bike Park, and the Frasier Valley singletrack network almost certainly make it the most well developed "High Mountain Setting" biking in the country. Numerous lodging opportunities exist at every price range, and prices are awesome in the summer. Same goes for food. You also have Rocky Mountain National Park and numerous other non-biking yet stoopid awesome things to do. Even if your a 100% XC type rider, i still recommend you spend a day trying out the lift service park and hit the moderate trails (blues and greens), unless you don't actually like riding bikes, you'll have a BLAST, and you can either rent a proper DH rig, or just ride whatever bike you brought. Lots of people ride XC bikes.
Moab: If you've never been to Moab, you need to go. Its one of the most insanely cool places i've ever been. its one of those places that it almost doesn't even matter what you do there, its just freeking awesome just to be there. Its also a town who's economy is pretty much 100% recreation based and everything revolves around Biking, Hiking, Climbing, Rivers and 4x4's. Its also almost entirely BLM land, and almost entirely unmanaged, and if you want to get off the beaten path and into no-mans land, its really really easy to do. I know lodging options exist, but i have never used them, and probably never will. 100% free, back country car-camping abounds. I highly suggest you have a high clearance vehicle, then you can pretty much head down a BLM road, and go camp. There are also a lot of marked campsites off the main road, but they fill up fast. I've not done much biking out that way, we go to 4x4 and climb, but the biking looks absolutely phenomenal. Call any bike shop to get the full Beta, there are also some really good trailmap guidbooks that tell you everything you need to know. Be prepared for a harsh environment, its cold at night, insanely hot during the day, and how much water you carry is pretty much always your limiting factor. Good food in town, and for a rest day activity i highly suggest you visit Arches National Park.
If you are ambitious, you can do both. Moab is about another 6 hours west on i70 from Winter Park, and the scenery on that drive is a worthwhile tour in the first place.