A few keywords needed upon arrival:
Cierre de plan de vuelo: Closing your flightplan (no FSS or FlightWatch- this is done at Despacho)
Despacho: Airport flight Dispatch.
Plan de vuelo: Flightplan.
Permiso de Entradas Multiples: Multiple entries permit.
Permiso de Entrada Unica: First entry permit.
El clima: Weather.
Comandancia: Local airport authority department.
Comandante: Chief, or person in charge of Comandancia.
Inspector: Inspector (assistants to El Comandante).
Migracion: Immigration department.
SAGARPA: Department of Animals and Agriculture.
Combustible: Fuel (note that Mexico uses Liters, not gallons, not pounds).
Torre: Control Tower.
Piloto al mando: PIC.
Llegada internacional: International Arrival.
Propietario: Owner (of the aircraft).
Sandwich de pollo: Chicken sandwich.
Con Tocino: with bacon.
-No visas required for US citizens-
No one at the airport (not even El Comandante) is allowed to retain your pilot license or medical certificate under any circumstances. They are allowed (and most likely will), however, get photocopies or photoscans of these, or any of your documents. This is very normal.
Upon arrival, you might or might not be greeted by Mexican Army or Navy, or both. One, or both, might or might not record everything on videocamera. This is ok.
Most tower controllers (torrero-double r) speak English. If no one at the Comandancia, or Terminal area speaks English, ask El Comandante to have "el Torrero" translate for you.
All of this should not be intimidating, it is only procedural, and most people are willing to help.
Expect people looking to take a picture next to your beautiful airplane. This is also normal.. Specially for the hard, under-the-sun working army folks.