within 4 hours of Denver covers almost the entire state, except the far NW & SW corners. Must be 2,000 campgrounds within that area; would help to be a bit more specific.
Bears, yes we have lots of bears in Colorado. Bears are more common in some areas of the state than others. My summer homebase is next to Rio Grande National Forest and I see bears every few weeks while camping or hiking or ATV'ing in remote parts of the forest. Just last Fri while I was riding the ATV down a steep hillside, as the trail leveled out on a bench halfway down, there was a big black bear 25 ft in front of me, busy digging grubs out from under a fallen tree. He looked over his shoulder at me, kinda gave me a look like, hey bud you interrupted my lunch, then took off down the hill.
Unless you're careless with food around the campground, they're usually not aggressive. One of our local NFS campgrounds was closed by the rangers last summer for 2 months because a momma black bear with new cubs were living nearby. We also have mountain lions and moose in the state and you'll read more news reports about mountain lion & moose attacks than bear.