I second the Row by Row experience. It has grown bigger every year and now includes shops in every state as well as Canada. If I was on your adventure, I would just google every town I was gonna go through and see what they had.
In the meantime, if heading south on Interstate 85 through North Carolina, be sure to stop in Gastonia NC at Mary Jo's Cloth shop. A huge shop with so much fabric it is almost overwhelming, almost. Here is a link to the store. Well worth the stop and so close to the interstate you can see the building from the highway.
http://maryjos.com/store/quilting