There are also some special websaver West Coast fares on AA.com. I haven't checked the prices but I am sure that they contain LAX-Seattle and even maybe YVR.

Also, you might want to consider buying a trip to Europe as the price will be usually the same if not cheaper and on such a fare you are allowed to go to both, LAX and YVR plus several other American connecting points. I've been doing this quite successfully for a while.