Yes it is true a lot of people get there early, and so many areas will be full. You will have no problem finding a place to set up camp, it just may not be in one of the most favorable locations (spots with lots of shade, etc).
Once you drop your gear off, you will exit the campground and park along the road. There will be a long line of cars already lined up, and you will have to park at the end. There will be lots of friendly people to help you/show you where to go.
The shuttle busses that run between Illium and the festival have to go past the campground and down the road where all the cars are parked to get to a spot where they are able to turn around. If you park you car and wait for the school bus to come they will give you a ride back to the campsite entrance. OR if you plan to be ready to go into the festival after you park your car, you can stay on the bus and go straight to town. Busses come about every 15 minutes or so.
Hope that helps!
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