ORP is only a couple hours from Portland, no need to stay overnight. But if you do stay overnight then just stay at a BnB right near the track in the town of Grass Valley or Moro.
http://oregonraceway.com/our-partners/lodging/
When I go out there to race, we're usually there for 3 days so I stay at the Crews House
Crews House Bed & Breakfast
541-333-2244
1006 SW 4th
TT: Nancy
Nancy is an old lady and really nice, but a bit like staying with your very religious grandmother, but who cares. She nice and next to the track!