There are two in Boise that I have visited. One is the Quilt Crossing and is located at the southeast corner of Curtis and Fairview at 5725 Fairview Avenue in Boise, Idaho. They are also the Bernina dealer.
The other is Quilt Expressions located at 9115 Chinden Blvd., #107 in Garden City, Idaho 83714. Garden City is part of Boise on the west side of town.
Both of these stores had really friendly staff.
Boise also has the JoAnn's and Hancocks, etc. There's another small quilt shop, The Country Quilter, in the Vista Shopping Center, but they were closed the day I was shopping.
If you are going north through Idaho and happen to go through Moscow, Idaho, they have a wonderful store called Quilt Something located at 705 North Main Street, Moscow, ID 83843-8511. However, when I went through there 3 years ago the staff was not very friendly or helpful.
Hope this helps. Enjoy your trip.