Does it have to be public? Can you not knock on a door and ask some farmer if you can hunt his land? If he is ok with that, see if you can do a little siting in of a scope.... You might be able to barter with the guy for the use of his land. Half the stuff you harvest, use of your guns when you shoot, cash, and old car you have, do his taxes for him. Be creative, but ask for the sale. All he can do is say no. Well, that and he might get mad and shoot you, but the chances are slim that would happen. Slim enough that I'm willing to take that chance.
As for where to shoot, a box canyon is perfect. That is a feeder creed that only runs when it is raining. you have a berm that completely closes your horizon. Safe shooting.
I shoot in my yard (box canyon) but hunt on a friend of my wife's land. I keep offering to "do" something for him, he just wants me to shoot any 'yotes I see. He is a chicken farmer. 90 acers of mostly woods. Backs right up to the national forest land that is the southern most point on the Appilachen trail, or the feeder trail anyway. Check out some wiki:
Amicalola Falls State Park is an 829 acre (3.35 km²) Georgia state park located between Ellijay and Dahlonega in Dawsonville, Georgia. The park's name is derived from a Cherokee language word meaning "tumbling waters". The park is home to a 729-foot (222 m) waterfall, making it the highest in Georgia.[1] It is considered to be one of the Seven Natural Wonders of Georgia. An eight-mile (13 km) trail that winds past Amicalola Falls and leads to Springer Mountain, famous for being the southern terminus of the Appalachian Trail, begins in the park.
BTW, the only "gun range" I've ever shot at was up at Knob Creek this year.