I would definitely spend several days in the Lancaster, PA area. Lots of quilt stores and great prices, plus you get a wonderful perspective on the Amish who live there.
There are also a lot of stores in the Buffalo/Niagara Falls area so if you go to see the Falls, check them out.
I hear Phoenix has great quilting stores. I'm heading there in two weeks and will have first hand knowledge then.
Also:
Rosies in San Diego
Pucky Huddle, Candor, NY
Material Rewards, Dansville, NY
Mary Jo's in Gastonia, NC (and one a mile away - Sew Much Fun)
Rainbow's End, Dunedin, FL
Fieldstone House, Sidney Center, NY
Stitcher's Garden, Franklin, TN
Keepsake Quilting, NH
Asheville Cotton Company, Asheville, NC
Batik Etcetera, Wytheville, VA
Calico Creations, Mt Vernon, WA
Circa 15, Kirkland, WA (mostly modern fabs but great store)
I'll warn you that I like stores with A LOT of fabric above everything else, and I'm not a fan of civil war or primitive fabric. I'm not looking for patterns, notions, friendliness, help; just fabric. So those populate my favorites list.
There are a lot of great shops out there that won't be on anyone's list because they are smaller or out of the way. So keep searching on your phone and check out the Row by Row site. Have a wonderful time and don't forget that when the RV won't move because of the weight of your purchases, ship it all home and start again!