When can I call in for the business upgrades?

I have a mixed itinerary flight booked on airtran with rewards credits that leaves LAS-DEN at 0555 am southwest on a tuesday. It then goes to CUN on airtran.
I want to try to use the two business class upgrades I have from the credit card, so I know I need to call in. My research indicates that I can call in at 12:01 (1 minute after midnight) on sunday night/monday morning. Is that correct?
And what time zone? My time zone, the time zone the flight leaves from (denver), or the time zone of wherever their service center is?
1-800-AIR TRAN is who I call?

Second question - My understanding is I can't book early bird check in for the southwest portion - so the only way I can get good boarding without elite status is to wake up at 0555 AM and check in on airtran.com?
There has to be some way to avoid calling at midnight for the airtran and then having to set an alarm for 6 hours later to check in for the southwest portion. And then repeat this for the flight back from mexico��

thanks in advance

I believe that the "calling in at 12:01am" deal went away when WN took over FL. Someone may want to check me on that. You have the correct number.

Sorry to hear that you may lose sleep. I'm thinking that you can just go to bed early, forget calling at 12:01am, set the alarm for 5:55am, check in with WN, and stay awake until FL opens and just call them then.

I would suggest that you call Airtran and ask. In many cases it is not necessary to disclose your name or your itinerary.

I called at 1201 and it worked.

I called after midnight EST. I called the 800 number and pressed "1" for flight information, connected to CSR. She upgraded me in seconds. It did not work earlier when I pressed the # for A+ Rewards members (i.e, no one answered/received "we are closed" recording)