Take Sound Transit 511 from Downtown to Lynnwood Transit Center. Then take Community Transit 113, 200, 201, 202, 118, 119, 114 to Alderwood Mall. There are like 15 routes from LTC to Alderwood.
Go to this website and enter the info in the trip planner. I use this religiously and it never fails. http://metro.kingcounty.gov/
The Lynwood bus from downtown, i think its # 535It s about 1hr 30m ride.