Mammoth Mtn. RV Park is approx. 1/2 hour from the Eastern Sierra town of Leeving on Highway #395. The turn off for Yosemite is just south (1/2 mile) of Leeving and that's Hwy #120, AKA Tioga Pass. The eastern entry point into Yosemite is approx. 27 miles up Hwy #120 on a very steep but awesome highway. The total trip to this entry point of Yosemite is less than 1 hour from Mammoth Mtn. RV Park. I've personally stayed at Mamamoth Mtn. RV Park many, many times and make the trek into Yosemite several times each summer, as there's some excellent trout fishing on this eastern border of Yosemite as well as some of the most awesome scenery you'll ever see. The owners of Mammoth Mtn RV park are very nice people, but try for one of the full hook-up sites in the trees, although many are reserved for the full summer each year. I hope this clears up the question of how long it takes to drive to Yosemite from Mammoth, but if you want to drive on into the Yosemite Valley itself (the floor of the valey) add another 1 1 /2 hours from the east gate on Hwy #120.