Wow, tough spot. I was stationed for 6 months in Idaho Falls back in the 70's while in the Navy (at the reactor training facility in Arco). Heavily Mormon community there. The backlash of coming out atheist would probably be severe (wouldn't stop me though). Good luck finding like-minded people.
I lived in Idaho from the time I was 5 until I was 26. I knew some atheists but, like me, most of them have moved to other places.
The Mormon influence was pretty strong in my small hometown and dating was something rare. I had a choice of converting to Mormonism or dating women who were... well, let's just say that beer and pot seemed to have a lot to do with their disposition.