Spend more time in Yellowstone than you planed, and Old Faithful is the WORST thing there, when at the Old Faithful from the car park walk past Old Faithful to view the other geysers there, check at the lodge for time when each geysers is due to blow, they tend to be pretty accurate , all the famous site are worth a visit and Mammoth is a must, I would say 3 days is a minimum in Yellowstone.
You'll get good shots of the Grand Tetons from more or less any where in Jackson Hole, I can't remeber where but there is a place where you can get the Snake river and Tetons in one shot, don't forget to turn round and get a shot of the Sleeping Indian, and don't forget the the Moulton barn along Mormon Row Road which is a VERY popular subject, and Bison do roam the back roads. Also check when the Elk come down to The National Elk Refuge for winter.
Check the weather as by late September you maybe getting some snow in Jackson Hole
Carmel will normally be 17 mile drive, if your travelling down the PCH then Hearst Castle is worth a visit IMHO
San Luis Obispo if your there on a Thursday get in town in the evening for the EXCELLENT farmers market (well it was when we were there)
Looking at your list , your trying to pack an awful lot into one trip
You'll need a NP pass for the car, we bought a full year one, and as we are tight that must be the best value for money option.
Get a map and look for the scenic byways on your route, Beartooth Highway in Wyoming is awesome and so is Going-to-the-Sun Road in Montana (a bit too far off your route for this trip) but see what you could drive along instead of the interstate
Do A LOT of research before you go as there is plenty of stuff that we never really get to hear that much about
Looking at your list you will be going left and down from Yellowstone, where as we went right and up, so we got
Thermopolis, Hot Springs, Wyoming,
Devils Tower
Deadwood
Mount Rushmore
Badlands
Little Bighorn Battlefield
Glacier NP
Yellowstone
Grand Teton NP (our friend has a house just outside Jackson)
People have different ideas on how to do a USA road trip, some plan, plan and plan, other like us have a start point and finish point, we don't book anything in between and just go with the flow, mind you that meant 4000 miles is 3 weeks
