I would add Inside Gateway to the list of good model railroad hobby shops. It is in Bellevue, across Lake Washington. Enjoy your visit to the Puget Sound area.
Northend Trains
http://www.northendtrains.com/intro.htm
Seattle's Train Center
http://seattlestraincenter.com/
In Kirkland Eastside Trains
http://www.eastsidetrains.com/
As for public layouts, try the Washington History Museum in Tacoma
http://www.wshs.org/wshm/model-railroad.aspx
Hope this helps!
dan.
im on vacation in seattle washington. i was wondering if any of you know of any model railroad displays or you have a favorite train shop in the area? thanks.