You're in North Georgia, so I'm going out on a limb here and stipulate there is pretty much no flat ground around there. Hills and constant direction wind never help your average speed on a course that ends where it begins - there are few absolutes but that is one of them.

If you are just transitioning over to cycling from running and averaging mid-18 mph on a solo ride with a lot of rollers, as stated above you would be riding 90% of the cyclists you meet on the road off your wheel.

Note also there is a change in your pedal stroke and the muscle development of your legs as you change over from running to cycling, especially on hills. When I had to give up running and picked up cycling, I found myself sliding to the back of the saddle to use more hamstrings as they were much more developed from running. After a few thousand miles and as the quads started developing more, I tended to stay more to the center.