Tri-Cities and the Eastern Gorge
Not fancy, but look for authentic Mexican if you like that sort of thing. Tacos Los Primos #2 in Yakima is great, as is El Manantial on S. Main Steet in Ellensburg. The place in Yakima is a funky Taco stand on 1st avenue, in a laundromat parking lot. Some of the best tacos I've ever had. El Manantial is a small, clean sit-down restaurant with a larger menu, everything made from scratch, burritos, sopitos, tacos, and more. The owner makes excellent Tamales on the weekends.