Pavilions rules are clearly posted for all to read on the side of the building near the drive thru. These have been the rules for as long as I have been going there (2004?).
For instance, up until 4pm (I think it doesn't apply during auction weeks) you can park-and save a spot on either side of your legally parked car. The folks I hang with primarily...get to the cruise between 8:15-8:30 am, as it's "first come, first saved" up until 4pm. We all park and sit together. There are days when we can't-and it's no biggie.
There are only two rows that are off limits to most folks. First is Corvette row-only Corvettes (any year is okay in this row) can park there. The second row is the row behind that, which is club row-which rotates every week to a different manufacturer. One weekend it's Oldsmobiles, the next Mopar, etc. This coming weekend it's Desert Derelicts turn-as Rick noted above.
Some of the other cruises (67th Ave for example in Peoria) allows folks to save unlimited spots and there is no time limit as far as I know. Rick may have a better idea-as I don't often go this this cruise, even though it's only 5 minutes from my house.