Hi, neighbor! I'm in Spokane. Lots of family in Yakima, though. Spent a lot of my childhood there, looking at those big pillowy hills.
Other than in yards and landscapes I haven't seen many juniper. However, I am totally new to bonsai, so I haven't really been paying attention to species in the wild until recently. But, I got BONSAI FEVER now. I look for nebari on every tree I see. I study bark and branches and foliage as I drive to work. Last night I literally dreamed about bonsai all night. I have a list of about 15 air layers I'm planning to start in my yard this spring. Yeah, I'm super hooked. My wife is bit worried, I think LOL.
But I degress....
I have spent a lot of time around Medical Lake and in the hills around Cheney. Best bet in those areas would be to find a gracious landowner, I think. My current yamadori hunting grounds are further north, in the Colville National Forest. I'm not looking to bring home any ancient/amazing trees yet, because i need to learn how to keep 'em alive in a box, first! So mainly scouting for now. Its also a great excuse to get out in the woods and play in the dirt for a while
Come over to my neighborhood. About 75 miles south, in Idaho, St Mary's national and Potlatch state parks both have great finds.
Hell's canyon has some serious junipers too but it's the worst terrain ever imagined. Bring a rope.