Also be sure to stop by the Washington county visitor center and pick up the county bike map. Also Beaverton and Tigard both have bike maps indicating roads with bike lanes, but also low traffic residential routes.
Here are some links:
http://www.tigard-or.gov/community/bike_tigard/
http://beavertonoregon.gov/index.aspx?nid=278
http://www.portlandoregon.gov/transp.../article/71794
http://www.portlandoregon.gov/transportation/39402
also depending on when you are here you could meet up for a pedalpalooza ride. Keep checking the site as many more rides will get added to the calendar.
http://www.shift2bikes.org/cal/viewpp2013.php