For a mature buck, you should hunt the western end of the unit and as close to the snowline as you can get or even in the snow if you're lucky enough to get some. The deer will not shy away from the north facing slopes because that is where the best food is but they will go to the south facing slopes if there is enough snow to make travel difficult.
Grew up in the Entiat and have hunted mule deer there since 1955 (as a 10 year old with Dad, brothers and uncles).