RE: Food in Fort Mountain State Park
Not that I'm aware of. I'm 85 miles or so southeast of there in Athens.
There's a great little cafe on the south side of Chatsworth on U. S. 411/76 named Edna's (I think it is), plus a couple nice places in Ellijay. You can try Poole's BBQ in East Ellijay or mosey up U. S. 76 east to Cherry Log (about 8 miles from Ellijay) to Pink Pig BBQ (I think I've got that name right).
Come to think of it, I don't think there's even any available water on Fort Mountain, unless they've managed to tap a spring someplace. Maybe the information you need will come up on Google... try it and see.
UnFortunately (GROAN!), Ort. Carlton in Lovely Athens 30601.
P. S. Good luck with your birding. They're starting to return home from down yonderways around here.
P. P. S. Since you posted this under "Pizza," I can tell you that you needn't depend on chains for pizza in Ellijay or Chatsworth. It might not be what you're used to in your home area, but the soft water running off a granitic underlay makes for good pizza-dough-making water (good brewing water, too!) -- we have a pizzaria here that's superb! Strikes me that someone told me of a decent locally-owned pizzaria in Ellijay... hey, if you can't find it, ask the police -- they'll know! I always do that when I'm on the road, and have never been steered wrong once.