My family loves Hershey Park and we go every summer, and at Christmas time. It is very clean, although hilly. It has to us a good variety of rides, DS13 and DH are big roller coaster people, so they love that. DS8 is not there yet and I could go either way.
I would not recommend going on the weekends if you can help it, during the summer it gets really crowded.
We try to go in June, when the crowds are not too bad, but when we have gone during July and Aug we stick to midweek.
They do not have FP or posted wait times, so I would get there early and get the headliners like Farhenhiet and Stormrunner out of the way first.
We also go up the night before, do the Preview Plan, and hit Chocolate World, before the Preview Plan. Go in at 7 or so, ride whatever we can or just wander around and develop our game plan, then go back bright and early the next day.