From Seattle:
Take I-5 southbound to I-90 east.  Follow I-90 east to the Columbia River.  Cross the bridge at Vantage and immediately exit to take SR-243 South.  Desert Aire is approximately 18 miles on the river side of the highway just past Mattawa.

From Spokane:
Take I-90 westbound to the Columbia River at Vantage.  Exit freeway before the bridge to get onto SR-243 south.  Follow the river for approximately 18 miles.

From Ellensburg:
Take I-90 eastbound until you cross the Columbia River at Vantage.  Exit immediately after crossing the river and drive south on SR-243 following the river approximately 18 miles.