I would second your idea of starting with the PCH route in April, especially if you have never done the coast. It's not to be missed. You will hit some rain in the Pacific Northwest but Oregon will be getting nice, and Northern Calif will be gorgeous. The section south of Carmel is stunning (see pic).. then cross over on Hwy 58 (a very nice road for most of the way) from the San Luis Obispo area to Bakersfield and on up toward Lake Isabella, proceeding northward from there.