It doesn't cost anything to sign up for FF programs, so go ahead and sign up for both AA and UA. The AMEX starpoints card allows for transfer to about 20 different airline programs, and gives a 5K bonus when you transfer 20K. I just found out, however on another thread, that you get 1:1 when you transfer to AA, but only 1:2 when transferring to UA. I vote for AA. In fact I am flying to San Diego on Friday from Chicago. I think AA has less expensive net-saaver fares and is pretty good to/from Southern California.