We are renting an RV in Phoenix for 9 days at the end of August. Our current itinerary is as follows: Sedona (1 night) Grand Canyon-South Rim (2 nights) Bryce Canyon (2 nights) Zion (2 nights) ...
We found the nicest RV park in Las Vegas. It's the Clark County Shooting Facility. It's only $20 per night, and includes 30/50amp service, sewer and water. At night, you have a great view of the city since you're in the foothills. Also, since you're above the valley floor, it cools down a little better at night. And if you like to shoot, they have a world class shooting range for very reasonable fees.