I've seen some trails near the Grayton Beach area in one of the parks, but I'm not sure they're mtb friendly. If you ride anywhere on Eglin, which is everywhere around the area, you'll need a Range Pass. Daily ones are cheap, even the annual isn't much, but they'll make you watch a short film - and it'll probably be easier to stop and get them before you get checked in at the beach. The issue office (Jackson Guard) is at 107 Hwy 85N in Niceville.
I'll be down there the end of this week, but with a road bike.
It's a little ways away, but I've seen quite a few mtbikers riding in Red Bay, and they finish up eating at the Red Bay Grocery.
Last edited by Ex Pres; 09-29-15 at 09:14 PM.