Read through the log of older threads and you'll get lots of great PDX advice on sights and restaurants! If you don't find enough info, let us know what your interests are and you'll get lots more advice.
You can also check out a huge list of vegan to vegan-friendly restaurants (plus sort by vegan-ness and area of the city,) and download a hard copy of a Veg Dining & Shopping Guide at:
http://nwveg.org/restaurants