As said previously reservations are not required for most of the nearly 400 parks in the Valley. Come down find a place for a week or 2 and visit many parks to find a park and site you like. All sites are not created equal either. You could get an undesirable site in a nice park if you make reservations without seeing the site.
Prices range from $150 a month to 900. a month + electric for longer term stays. I also suggest you check out the many parks on Bentsen Palm Drive South of Palmview.
This will not be a normal snowbird year as many of the activities and entertainment will be canceled or modified due to Covid 19.