Jonathan,

Are you flying, or driving? If driving, they won't care one bit. However, you'll have to deal with the rather unpleasant demeanor of most border crossing guards. Driving does have one advantage, that being the ability to hit up places like Glazer's and Kenmore Camera on the way down (and/or back).

I've had no problems shooting in the city of Portland (as well as, obviously, here in Seattle).

-J