I agree that you don't need a car at Reed. The bus takes 15-20 minutes to downtown, and there are plenty of shops, etc., close to campus.
As an example, I asked
TriMet: Public Transportation for the Portland, Oregon, Metro Area how to get from the PDX airport to Reed; one trolley and one bus get you there:
Starting from (Airport MAX Station) Portland Int'l Airport MAX Station
12:56 p.m. Board MAX Red Line to City Center & Beaverton TC
1:16 p.m. Get off at Hollywood/NE 42nd Ave TC MAX Station
1:30 p.m. Board 75 39th-Lombard to Milwaukie TC
1:48 p.m. Get off at SE 39th & Knight
Walk 0.4 mile west to Reed College (3202 SE Woodstock Blvd)
Travel time: 66 minutes (including 14 minutes walking and 14 minutes waiting)
Fares: Adult ($1.75), Youth/Student ($1.40)
There's also the usual door-to-door shuttle for about $28 one way.