I would be very grateful for any advice you could offer on routes. Me and the other half are going from Chicago to San Francisco, over 17 days in September. We will be spending 2 nights each in Chicago and SF, but other than that the route is fluid. Ideally we would like to visit at least one National Park. As I see it- we could go more northerly and do Yellowstone and Lake Tahoe, or cut South and do Grand Canyon and Yosemite. Is there any particular route that would be of special interest do you think? In particular I'm looking for advice on where would be good to visit as we cross towards the NPs. Sorry for such a broad question!!!!