Unfortunately just Thursday-Sunday.
April begins the "high tourist season" in Oregon. However, there are lots of great hotels in Salem though. Salem is a great place to stay as it is an hour from the coast, an hour from the mountains and an hour and a half to the high dessert. Also much less traffic than Portland, although the Japanese, Chinese and rose gardens there are certainly high on my list of must-sees. Just don't go there at rush hour!
Kevin