No can do...they will chase you out of the lot. First security, then the cops.
If you leave your car there overnight, however, they are OK with that. The only thing is that they often will (believe it or not) tow all of the cars that were left overnight to one lot, or move all the cars into one area of the lot that you left your car in. That's really dependent on what's going on there the next day though...if there are no shows they will leave it where it is...if there is another show coming they will likely move your car to avoid any parking issues the following day.
If you plan on sleeping in your car, your best bet is to not park in the lot, but on the side of one of the service roads leaving red rocks where they often allow you to park. I don't know if it's a property/liability issue that disallows sleeping in your car, or simply the fact that they'd like to move your car and are unable to do that with you slumbering in the back seat. But, either way, they don't seem to pay much attention to cars left on those side roads overnight.
edit: it's sounds like you may have to park pretty far down so that you are basically out of park space in order to not get hassled. I've done this before after getting kicked out of the main lot, and was able to crash overnight. But I can definitely tell you that I have no recollection of exactly where I parked, lol.