I think that in order to view the seatmaps at the MX
website, you need to do a reservation; just did it last week. I also recall seeing seatmaps in the last pages of the print schedules (still available at the airport counters), though I guess that is not much help. You know who will help? Logan (aka N405MX). I'm sure as soon as he reads this he'll reply with info.
Next flights: MEX-LAX AM 738, LAX-PVG DL 77L, SHA-PEK CA 789, PEK-PVG CA A332, PVG-ORD MU 77W, ORD-MEX AM 738