There is a Yahoo group that is devoted strictly to rentals for the Sisters Show. I got a great 3 bedroom house, 5 minute walk from the quilt show a week before. This was 2 years ago, but on the list they seem to have stuff available up until the last minute. I think I only paid like $200 for two nights, too.
There are day trips advertised from the Seattle area, I think I saw one advertised at a quilt shop in Bellevue last year.
Here is one that is a two day trip:
http://www.toursbydiscovery.com/t_de...p?recordID=821
I know that Fabric Depot in Portland does a bus trip, so if you could get to Portland by car, train or bus you could go from there.