As a rule of thumb, Western Oregon soil is acidic and the winter rains deplete nitrogen levels. Temporary changes to soil acidity can be made, for example lime applications are often recommended for lawns, and nitrogen applications can be timed throughout the growing season.
This selection of articles from the OSU Extension catalog covers various details of more comprehensive soil testing and considerations. Your choices of testing really depends on what you want to plant. Drainage and sun exposure are big considerations as well. Feel free to ask specific questions as you go forward with plans.