This area requires a permit which you can buy at the ACE hardware in Nederland. However, after mid-September permits are no longer required or sold, as we found out when we arrived at the hardware store.
We camped about a mile down from Devil's Thumb lake because we got a late start (~4:00pm) and it started getting dark and cold. We made the hike into a two-day loop instead of out-and-back by summiting and then taking King's Lake trail back to the original trailhead. Beautiful sights all along this path! It's about 12-13 miles this way.
Plenty of access to water via various streams. Did not see many other people camping. Passed a few hikers the second day. Once you summit you can see the town of Fraser and also get cell phone service, but we did not have service in the valley before summiting. Note that it got quite cold this night in mid-September, just below freezing.
We arrived at Zion on a Thursday evening in mid-November'19 without any plans. The Zion South Campground is closed for the season at this time, which we were unaware of. We did not have a reservation, and the sign at the entrance said full. We drove around a bit anyway.
In the 'F' loop, which has access to the walk-in sites, we noticed a parking spot without a reservation tag. So we knocked on the door of the on-duty campground host to ask about its availability. Sure enough, it was a no-show and they allowed us to stay after paying the standard $20 fee. The host made sure to explain how rare this occurrence is and we shouldn't bet on it in the future. Worth a try though if you have no other plans!
It is a very short walk from the parking lot to the 'walk-in' campsites. Maybe a few hundred feet. Sites are pretty close together, and the walk-in sites do not have their own fire pit. Instead, they have a few communal fire pits with benches around.
The sites each have a nice flat tent pad, an awning for shade, a picnic table, and a bear box.
Stayed here for a night before checking out the Delicate Arch at sunrise. Works pretty well for that as it is only a 10 minute drive to the entrances of Arches NP.
We didn't venture very far down the main road, and at the beginning it is pretty dense with campers. Probably not the best choice if you're looking for more secluded camping.
Mid-November it got down to about ~30 degrees F. Down to ~24F when we entered the park at 5:30am.
We had a group of 14 people camp in the dispersed camping area off of Hohnholz Lakes Rd overlooking the lake. Really great spot, plenty of fire rings, tent spots, and some nice log benches. I would recommend bringing your own firewood for the dispersed area, unless you have an axe or chainsaw. They also sell firewood at the regular camp grounds.
The lake make for some good swimming during the day, there's a nice beach spot on the Northeast side of the lake, just drive a little farther down Hohnholz.
Note that no one in our group had cell phone service for most of the drive up the Poudre Canyon, as well as at the camp sites.