We did contact someone and here is the message we got.
"The Cruise In is held on Saturday June 4, 2011. Food and street dancing throughout the evening with all types of cars on the courthouse lawn for viewing. Cars are given awards in different catagories. Bring a lawn chair or blanket for seating."
So if you are interested in showing your car, per the link below, contact Larry Gossett at (765) 344-8109 to register your car.
Main Street Rockville - CRUISE IN JUNE 4 2011
Chances are those of you with the mods and obviously near garage princess condition would be contenders.