Pediatric Associates of the NW has two offices: NW 25th and Lovejoy, and off of Kruse Way. Most of the doctors work alternate between offices. They are open on weekends for emergency appointments. Our Dr. is Schunk, who has been great with all kinds of advice (health and behavioral) and I have also seen some of the other doctors when he is not available. All have been great. You might want to check out their website.
Also I have heard that Dr. Prichard in Sellwood is good.
I strongly recommend that you narrow it down to 3 or so options that seem to fit your needs (hours, location etc) and then see if you can schedule an informational meeting with the doctors before you make your decision. You'll want to make sure the Dr's personality and philosophies (immunizations, developmental issues, etc) are a good fit for you. Many drs will schedule an appointment of this nature before or after office hours. In my opinion, the Dr. should want to make sure it's a good match as much as the parent does.