Congrats on getting these great choices. I happen to know most of these cities I can tell you that depends on where In the world you live right now, Phoenix weather is intolerable most of the year for many. CPSLO, SC, SD are a lot more pleasant to live. As for partying. You seem to be very specific about schools with not enough parties vs too much parties. You didn’t say quality vs quantity. To me, I like quality over quantity. I can honestly share with you that the parties are whatever you make it. First of all, you can’t expect to party all the time as a serious student that wants As or Bs only. On weekends when you want to join big parties, those schools with 10s of thousand students are bound to have parties, it’s how you want to make it happen, and Depends on if you want to have a nice party, or the party that end up badly. Also there’s nothing preventing USCD students from partying with SDSU kids. There are Greeks in UCSD just not on campus. Santa Cruz is nice just colder than SoCal. If you are making the big investment of 4 years of your life, I highly recommend you to make a small investment to visit before deciding. It’s a personal choice and others won’t be taking your consequences.
Please do not reopen such old posts. The OP would have decided long ago.
Closing.