We have boondocked in the designated overnight RV parking area several times. We left our toad home since we had no intention of traveling around. In the past years it was $25/night. The area is well lighted and a short walk to the show. You will need to find a level area since most of the parking lot is not level. Generators are allowed to run during specific hours. We have found it convenient since our purpose is to see the show.
Note there is a daily RV parking lot also. In the below ref. web site there is a site map of the show to locate RV parking, vendor and RV manufactures.
This is the Hershey RV web site for your info:
Safe travels and THE JOY IS IN THE RIDE