The "unofficial" answer is that pretty much if a place isn't posted in PA, its fair game. I don't want to debate the right or wrong of it, I'm just telling you what's typically practiced.

Now the right & safe answer would be to contact the town/township or whatever and ask what the land is designated as. If you already are certain it's state land, its just a matter of seeing if its a park or some other designation that would make it off limits for hunting. But also be prepared that if the local cops or whoever use it as a honey hole, they may toss you even though you are completely legal.

Good luck