As an Auburn native, feel like I should help you out!
As stated, you can find grouse pretty much anywhere north and east of Hwy 2 in that vicinity. Good time of year to be there, the grouse will be in the gravel roads in the morning and evening. Just drive. Derby Canyon, Eagle Creek (if the fire gets put out), Van Creek, Second Creek, Little Chumstick, all the mentioned places around Lake Wenatchee...there's grouse in all of them, you just need to put in some miles.