I was with some friends this past weekend who saw the Mt. Joy show at the Yarmouth Drive-In a few weeks ago. They said it was fun and they were psyched just to be at a live music event again, but they were surprised that the audio was through their own car radio (like a real drive-in) and the couldn't really hear it well if they left their cars (like if they just wanted to sit in chairs next to their cars). That's why we were curious about the set up at South Farms in Morris, because that is not a drive-in, so it would seem that they would have to have real amplification through amps, speaker towers, etc.
I believe they also said no booze was allowed, and none was for sale.