My girlfriend and I have a ton of friends and family that visit us, and one of the favorite afternoon of everyone is 23rd. Without hitting the coast or St Helens, a fun, relaxed stroll through 23rd and the cool shops there do the trick.
Givs you a flavor or what Portland would love to be seen as - hip, diverse (kinda), and unique. Shops for everyone - from coffee lover, chocolate shops, clothes, shoes, body/face make up & such, to a great record shops and the Monkey shops.
Just a fun afternoon and a favorite for us even when no one is visiting.
Pros: a little of everythin, g, snacks
Cons: parking, no great dining