If you've never seen Zen's bus Homer, well let's just say it would make your Ghia look like a show car. Definitely bring it if you can, but I do think they are predicting rain for Friday.
You can just show up Saturday too and just the fact that you'll be driving an air-cooled VW means they'll just let you in. Paul told us we will be parked along the north end, whichever end that is I'm not sure though. I won't be there Saturday anyways. Just show up around 10:30 and keep in mind if you park on the bridge, you will be pretty much locked in all day until 7pm. If you want to park where you could get out earlier, there's going to be another section in the park near Greenlife and Mellow Mushroom's tents.
On Sunday you can just show up around 10:30 and find a place to park. I think they will have a spot for us out front. Carter St will be closed so there should be plenty of room, there's also a lot to the side of the Pavilion we should have access to.