I just wanted to say: Walmart deserves credit for being very cool toward travellers. We spent many nights parked for free in their truck spots.
Walmart gets a lot of hate here in the bay area, but I really like them. If I may wax philosophical for a minute... I see Walmart as basic infrastructure. They are everywhere; they're always open; they sell everything, nearly at cost; they employ 2.2 million people, many of which would otherwise be on welfare or disability; and when you need a place to spend the night, even if you find yourself in Winnemucca at 1am with a 40-foot long vehicle and no RV park reservation--they're always there for you.