I don't care for densely populated campsites, but don't want to be off in the middle of nowhere alone either. Feel safer when there are some others near by.
That said, I started today at the Plomosa Road Campsite which had a host on site, required registration, but was free. Quite a lot of RV's there. Went 2 to 3 miles further and was in the BLM dispersed Camping area. It was much nicer, had good cell signal, but was flat and plain terrain. Continued abut another 10 miles on Plomosa Road and came across a historic marker called Quinn Pass, then continued about another two miles and found the perfect spot I was looking for. Very Scenic, dispersed campers, but not to many and good phone and internet coverage.