Flying SJD-MEX-BJX next month and trying to ensure UG process goes smoothly. I booked directly through AM and have my and my companion's SkyMiles #s attached to the PNR. When I called to request a manual add to their upgrade list I was told I should wait for an email to arrive 'a week to a few days' prior to departure at which point I should call them to opt-in to any upgrade. This doesn't seem correct so curious if this guidance is accurate and/or what, if anything, I need to do. Ticket is booked in AM+ fare class and I'm GM with DL.