Hi and welcome to RTA !

The more you can tell us about yourselves and interests the more we can help. Are you residents of SF or flying into there to start ? I presume the latter as you say "Finish in Texas" so I presume you plan to return home from there. With the amount of time you have available you could actually create a loop trip seeing different things out and back and possibly save money on one way rental fees and flights. Las Vegas is an experience in itself but might not be to everyone's taste so whether or not its worth it is a personal choice, but you could also visit nearby Death valley, Valley of fire and Hoover dam amongst many other attractions, perhaps along the famous stretch of route 66 through Kingman and Seligman to Williams and visit the Grand canyon. (weather permitting) Joshua tree, Petrified forest and Big Bend National parks come to mind but there is so much to choose from. Have a look around the RTA site, you will find lots of ideas and info in areas such as the Roadtrip field report forum, the RTA maps and by scrolling down this page for 'Similar threads'.

Once you share more info and have specific questions we can give much more meaningful advice. Enjoy the planning, it's a fun part of the adventure !!