i think MIA is the only one they wont let you choose now? But that is just what ive heard. All others are open. You will be on reserve a while if you go to LAX or LGA... probably a year at LAX and maybe 5 or 6 months at LGA. ORD is the most junior, you probably wont be on reserve for more than a month there. BOS and DFW are fairly junior too, you should only be on reserve for 2 maybe 3 months or less. I have no idea about San Juan.