just stayed at a walmart a week ago, for about 6-7hrs (something like 1am to 8am or so). There were signs posted, but 2 trucks parked and another RV. also a security guard circling the building constantly. The guard could have easily told us to move on, but didn't even stop. We stayed at this walmart based on information on
this site. We were way back in a corner, near the tire/auto shop area. I figure the signs are a liability issue in a lot of cases, but we had no issue at all. Didn't bother anybody, nobody bothered us, on the road nice and early. And we did pick up a few things in the store.