Hwy 20 is definitely the way to go. it has been warm and clear statewide for weeks, records for no rain. consider taking Hwy 20 all the way west, down Whidby Island, and then hopping the ferry over to Mukilteo, then short ride to Seattle. camping is available at Grand Coulee, next to the water, and at Bridgeport and at Alta Lake. all sorts of campgrounds on going north thru the Methow Valley, and a couple of Inns in Twisp and Winthrop (Twisp River Inn is new and highly recommended). do not miss the little store in Mazama just before the passes, really good food there. dust off the granny gear for Washington Pass and Rainy Pass, going west on 20, several forest service campgrounds to choose from, and state parks on the west segment of 20 and on Whidby Island, should you choose to go that way. the campgrounds are generally open thru October, or until snow closes Hwy 20. you are right, hwy 20 is much better for cycling than hwy 2.