One of the best kept secrets of Colorado is that any land considered public (BLM, NPS) is free and open to said public. That means that as long as you've pitched your tent on public land, you're okay. It's called dispersed camping. It may limit your ability to burn a campfire, but it has its benefits too.
As pointed out, a lot of those regions are subject to ATVs, dirt bikes, and the like. Again, as long as you're on public land and are following the rules thereof you're pretty much a free spirit.
You'll want to come in from the Grant side, though, as the Guanella Pass/Georgetown approach is impassable because of road construction. Much prettier route anyway.