Several people out here at Rancho California RV Resort in the city of Aguanga (east of Temecula) rent their spaces out on a month to month or daily basis if buying a lot doesn't appeal. We own a lot and move back and forth between Orange County, Aguanga and other points. I need to be local to O.C. a couple weeks out of the month. A couple O.C. places we stay often are Newport Dunes and Canyon RV park in Anaheim both rent long term spaces by the month, weekly or daily.
As for a list, I don't think there is one for just long term spots. it's more like hunt and peck, simply call them and ask what their terms are.