I have biked from Seattle to the Bay Area a half dozen times during the time period you are contemplating, and I used the Vicki Spring/ Tom Kirkendall book. Oregon also produces a very good and informative coast bike route map. The Oregon Department of Transportation Pedestrian and Bicycle Program distributes the map for free (or at least they did distribute for free - things change). While the book may be outdated, the route suggestions are not. I suggest you take advantage of those suggested routes that take you off of U.S. 101, particularly the section south of Tillamook on the Oregon Coast and through Coos Bay. Crossing the Astoria Bridge over the Columbia from Washington isn't fun (no shoulders, narrow traffic lane, and no sidewalks). The two tunnels on the Oregon Coast are not a problem, but be sure to activate the "Bicylists in Tunnel" lights, and don't dally. In general, the Oregon coast route is great - good shoulders, good scenery, good state parks. California is a challenge and not as bike friendly as Oregon. U.S. 1 in California, particularly in Mendocino, Sonoma, and Marin counties, can be narrow, no shoulders, and a great deal of RV traffic. Be sure to use the suggested alternate routes throught the Redwoods in Northern California (Avenue of the Giants as an example). Washington is also a friendly biking state. As to the weather during September/October - September is a good month; October can be iffy if you like to ride without layering.