Yes, a day at Yosemite is certainly better than never getting there. However, a day might not be enough to see all you would like to see. With the crowds and the roads, it's a little difficult to get around. Will you be pulling a sightseeing vehicle or a trailer that you drop so you can sightsee? Makes a big difference is how much you get to see in the various parks. Also, I think you might want to skip the cities you have listed, Las Vegas and San Francisco as they are just cities and will take away time from seeing the beautiful sights of our country. We took a 20-day trip last May from our home, Lander, Wyoming and hit Nampa, Idaho to see grandkids for a few days, Elko Nevada to see some of wife's extended family, Lake Tahoe for a day and a half, Yosemite for 2 1/2 days and Sequoia for 1 1/2 days before heading to Palm Desert and then back up through Zion and then home. We put 3,800 miles on the truck and about 3,400 miles on our FW. If you have only six weeks, I would suggest you narrow down your sights to really wondrous ones rather than stopping in cities. Just my two cents. I would also have suggested you take in Yellowstone and Grand Teton National Parks, Black Hills, etc., but your suggested itinerary just wouldn't be able to fit that in. Maybe another trip in the future?