I cross back and forth on a regular basis as a US citizen married to a Canadian with lots of family in BC. We live in Portland. I don't remember a border agent ever even mentioning photography and I always take my camera and lots of film.
As to shooting in Portland, no problem and it has a lot of interesting areas to shoot in. If you make it to North Portland to an area called St Johns you will find a great camera store that specializes in analog and has a tremendous used camera department and even does optical printing for your color film.. it is called "Blue Moon". Walk from there to Cathedral Park for some interesting views.