ive done the RAP - DEN drive a couple times when i lived out there. the five hours it took to get to denver was worth saving over $200 when flying home to wisconsin. your going to need a car if your going to rushmore and the surrounding areas. its a great time out there, the drive through custer state park is most excellent. id suggest if you have some time to stop out in deadwood its a great old west town. have fun, im a bit jealous i was hoping to make the drive out there this summer, but have now run out of time.