2012 Grizzly Classic in Salem is open to all K-12 players. Play will be divided into several sections, so the tournament is suitable to young novices and strong high school players as well. Affordable entry fee: $10 (with $5 late fee).
Green Coquille is primarily scholastic but is open to all ages. Affordable entry fee: $10. Not from the southwest coast of Oregon? No problem. Some local families would love to house out-of-towners, and there are local hotels.
Spring Open at the Portland chess club is open to all but is intended for adults and mature scholastic players who can sit for 10-12 hours of chess for two days in a row.