Off Pavement wrote:
If you can go in April, why not go where few folks go, and those that do wish they could go again... Death Valley National Park.
For renting a RV a first time, this would not be the place I'd recommend. :) Besides, right now roads are washed out and Scotty's Castle (a main attraction) is full of mud and may take months to clean up.
I'd recommend flying into Idaho Falls and renting from there, if possible. Then drive up to Grand Teton Nat'l Park and Yellowstone Nat'l Park. Late May, early June would be ideal before the major tourist rush begins.