We've been fulltiming since January and this was the first place we actually stayed the whole 14 day limit. Perfect location for exploring the Black Hills and so much fun exploring to do just at camp. There's a homemade sign that says no fires upon entering and a ranger confirmed that fires are not allowed out here, pit or no pit.
For starters, take North Pole Rd from 16. Renegade Pass is also an option, but we liked the other road better for the motorcycle. I believe you can camp along the whole road, but the real RV camping starts just past the Renegade/North Pole Rd junction.
I'm sure the best site for phone service would be the first site on the left on the top of the hill, but it gets windy up there. That's also the best spot for group camping. We camped nestled in the trees in the second campsite on the right, just past the one that goes down the hill.
There is room for multiple rigs in that area, but the spot just to the left when you pull in had the best service and was our favorite. We originally were in the turnaround at the end until a 40 ft 5th wheel showed up one night and set up right next to us, bringing their tent camping friends and zoo of children along. Upon moving the next morning we learned that the service was much worse at the first spot.
There are plenty of spots all the way down the road for rigs of all sizes, but don't expect to find a good spot on the weekend. People were cruising looking for spots everyday we were there, with some disrespectfully cramming in.