All of my travel to MEX over the last 5+ years has been to T1 where one must exit the Aduana (Customs) area into the land-side (non-sterile) area of the airport. I seem to recall similar setup in T2 - I do not believe there is a way to go from the sterile Aduana area directly to the sterile gate-area but my memory may be faulty or they have changed the setup - hopefully someone knowledgeable can comment on that.

If you do not have checked baggage then upon arrival at SJD/PVR you might well be able to go directly from the domestic flight to the AS gate to check-in for that flight - I don't know as I do not know that airport. Probably worth a call to AS to find out.