As far as best timing for golf in Oregon, the summer through early fall is generally reliable. But often the state of Oregon and the Portland area gets a bad wrap about being raining because that is usually the thought associated with the area. That is just not the case. There are many sun filled days through out the year. I particularly love the golf experience in the early fall. The trees with their colors and the smell of nature and its beauty wraps around your mind as you track around the course. Really a fantastic experience.
One of the most reliable areas to travel for golf with assurance of super weather is Central and Southern Oregon. Central Oregon has over 30 some courses with a wide variety of designs and price points for greens fees. And, it is filled with sunny days. Southern Oregon too has a super collection of courses and more reliable weather in and around the Medford area.