Hi, Audrey. We do the long diagonal. With the Casita
it takes 12 to 13 hours from Jonestown. We stay with friends in Santa Fe, but I'm pretty sure they have electric hook-up at Hyde Park (NM state park), which is a little ways up the ski area road.
I've heard the state park at Santa Rosa is nice, but haven't tried it yet (it's so close to SF, that we always just push onward).
Last year we stayed at the SP on Lake Colorado City (Texas, just south of Sweetwater). It was okay; far enough up the road to be worth the relatively late departure the next day... a bit strange, because it's across the lake from a huge power plant.
When I was a kid my family used to camp at Monahans Sandhills SP (near Odessa, TX). I have great memories of it and would like to go back.
There is a cg south of Clovis NM that we've considered staying in before... but, again, we always just keep pushing northward.
And then the other possibility might be the SP on Lake Sumner.
I'm actually quite interested in the answers you get to this. We've been looking to vary our trek to Santa Fe... it's a drive we make a couple times a year (not always with Casita