Phoenix Fire Games (it shows up when googled, and has a facebook page if you are into that kind of thing) is my go-to FLGS in the Boise area. It's technically in Meridian, but the two cities might as well be one because they are right up against each other (the shop is only like 2 city blocks outside of Boise).
The one thing that can be confusing about getting to the place is if you are using a GPS and don't correctly enter that you are looking for an address on East Fairview in Meridian, rather than in Boise, because Meridian is west of Boise and both cities decided to use the east/west split, putting two streets called East Fairview on the map with a long stretch of West Fairview in the middle of them.