On another forum here, I saw a thread about Cornish walls. It looked interesting, but finding the appropriate stone to make those walls would be the challenge.

I have seen boxwood do well in Boise, so I suppose that would work, but you might consider using arborvitae or cedar to get year-round privacy.

I have a soft spot for rhododendron, but they need acid soil, or at least inoculation with mycorrhizal fungi and a reliable supply of water during the hot months. Plus, they don't grow very tall.

I also live in Eagle and currently trying to accomplish the same thing... gain privacy. One of the problems we have is too much water, so we went with the Yew because they can take more water than most plants, they're easy to care for and I like the look... it's much softer to the touch and the eye than most plants. I am having to learn all over how to garden, because the climate and soil is much different than I'm used too. Let us know what you decided!

Deb