There's nothing like sitting in the socal/Yuma/Quartzsite desert with full sun, 70 degrees and a 1000 watts of panels looking at the sun.
The worst thing that happens is wind storm but I'll take that over snow and ice. I've also spent time in North Central Florida and it's fine during most days but did hit the 30's at night. The difference with being in FL, ga, s tx, s az is that you can have poor weather for a particular area compared to other years but none of them go into deep freeze with frost in the ground.
When it gets real cold, being in an RV is like being in a slab house in North Wisconsin. I've been in the Houston area and seen a barely visible dusting of snow and some days of ice on cars but the majority of the time it's a light jacket or tee shirt weather.
You don't want mountains even in places like Flagstaff. It sits at about 7000 ft. We go to Flagstaff around the beginning or mid November until it starts hitting the 40s at night. We then move down to cottonwood then Congress then Quartzsite.
Cell signals and ota television can vary. We use a satellite for television and have Verizon cell. Out west the cell signal can be blocked by sitting behind rather small mountains of less than 1500 ft or so.
We are also tree people and at first it was strange being out in the wide open but you can't beat it when pulling an RV. A lot of places in those warmer areas don't have a lot of trees. Some areas have more like scrub trees and large bushes.
I can't tell you about RV parks because we just about always boondock. There are also private owners in places like the Yuma foothills that rent out their small lots. Some are just a bare lot and some might have a small building with a washer and dryer etc.