We joined PA last year and our savings on a 3day camping trip paid for our years membership. We have only used it at three campgrounds so far, but we have saved a bit of money.
Now, having said that -- it may not be for everyone. Go up to PA's website (looking is free) and look around to see if there are any participating campgrounds in the areas you plan to go. Pay attention to the restrictions as many have limits on # of nights using discount or restrictions on time of year or holidays.
If you see enough campsites that you will use to make up the membership then it's a good deal -- otherwise . . . --
I'm turning 65 this year so i'm sure all the over 65 discounts will disappear
Tim