I know that for many US cities, a car is either required for all sightseeing, or for most sightseeing beyond the basics. (Covered by questions such as these). However, I hear that Portland, Oregon is a little different to many parts of the USA, and walking + public transport is much more common there.
I'm going to be in Portland for a conference, but I'll hopefully manage to squeeze in a day or two of sightseeing around that. For a few days sightseeing, covering the most common sights / attractions / short walks etc, can you get away without a rental car in Portland? Or should I be looking at trying to snag a cheap rental deal for at least some of the time?