Natural wonders of the world !
Hello and welcome to RTA !
As glc mentioned you will find a wealth of info throughout the forums, here's some of our favorites to get you started.
You will need to work out how much time you wish to spend in each City and see what time remains. Two weeks could certainly be enough to add a couple of natural wonders to your trip. From San Fran you could head to Yosemite NP [a true gem] before heading back to Monterey and the coast. From San Diego you could head to the South rim of the Grand canyon and then to Vegas over the Hoover dam. An overnight stop on route to GC would mean a little time to explore along the way, possibly a trip through Joshua tree NP.