For about a week now, a new truck has been dishing out the goods in the Winchell's parking lot on 45th, just east of Dick's. It is called Rancho Bravo, and was formerly located in Kirkland, according to the cashier (there are now 2 other trucks in Kirkland operated by the same proprietor, she said, and a brick-and-mortar taqueria planned for Bellevue).
They have all the usual tacos, tortas, and burritos. I had one taco each of carnitas, asada, and al pastor, and they were all of fine quality. The fresh salsa roja and verde were nice, and there was an exceptional spicy yellow-green one.