The McMenamins Kennedy School is a former school turned hotel. It's less Ace Hotel and more, well, something not so hip. That's a good thing. You won't find overpriced cocktails or Budweiser tallboys (not that there's anything wrong with that). You'll just see a few families and hotel guests warming up from the chilly PDX weather.
The pool is in the spot of the former teacher's lounge and access costs $5 for visitors (free for hotel guests) and is a must when visiting PDX. Highly recommended on a cold afternoon.
For more PDX recs, check out Huckberry's Field Guide to Portland. I visited the Kennedy School pool while helping to put it together.