It’s an easy trip to many of the ski areas, and in the fall in particular, the hiking, biking, etc are great and accomodations tend to be more affordable. Park City is very accessible to SLC airport and has great food, shopping, spas, as well.
Like many, I’ve done Nashville with girlfriends. Definitely fun. I was less excited about Austin but we had a good time.
Santa Fe is trickier to get to but also lots to do (everything from art – making and looking -, hiking, cooking classes, etc.)
It’s not a great option from CA, but New Orleans is fun if you’re into music and food. Agree that Charleston and Savannah are options.
If you like to explore cities, Chicago and Philadelphia are both great options.
I travel with friends a lot. One cohort is very outdoorsy and active, so having those kinds of activities is the driver, with good food and a spa treatment or yoga class for recovery being a plus. We do a lot of talking while hiking, and we don’t all live in the same place, so the gatherings are first and foremostabout reconnecting and second about how we do it. The other cohort is much more interested in cultural activities, so places with good museums, architecture, history, etc are of greater appeal. Getting the right place for your group is very much about what the group wants.