Originally Posted by channa
UA sells SFO-SEA for $178 RT on your dates. AS sells OAK-SEA for the same. I would just book that and drive up. Use your miles when you know they're in there, and for a more expensive trip.
You can save and use your miles to book SFO - East Coast via Seattle sometime in the future. Boston, Newark, Miami, Orlando, and could even be booked at the last minute. Sat - Mon rental cars are very inexpensive and it is 2.5 hours to Vancouver but allow extra time for the border on Saturday afternoon. If your can do the one-way it is $245 for SFO - YVR/SEA - SFO so you don't have to mess with the border on Saturday.