I use to go there during the winter in the 80's. It was legal to camp , but I think the beach wasn't designated yet. We went anyway, as it was absolutely amazing for us northerners to be on that white sand beach and dunes. Lots of raccoons, along with the deer. If that's still the case, I'd think about protecting my food. As this was before bear cans, we used coolers strapped to our pack. We didn't find useable water, brought our own liquids. I think you'll find they recommend you do just that.
Trout fishing was good to excellent. Up north we call them weakfish. I'm so happy to hear it isn't destroyed. I've been told that the stretch around Mexico Beach is wall to wall condos, so I figured the park would have succumbed to some kind of glitzy development. Have a wonderful time. Could you please put a report, and maybe some pics on this forum?