recommend handler for "first timers" to Mexico, once you do it a few times and you get to know the airport people, you can then do it on your own.
Mexico is way chilled out, don't believe all the stories. Shake hands with everybody and smile and say "Hola" to everyone and you will be fine. If the soldiers want to search your plane, let them. You are on their turf. The are NOT going to plant anything on the plane.
If you have some coca-cola's in the ice chest, give them to the soldiers and they will love you.
This forum below is all Mexican pilots and students, post your same post in English on this thread, "Aviacian Real" and give it a few days and you will get any question about Mexico answered.
http://fsmex.com/foros/viewforum.php?f=2&sid=91092a025de86058c8218d6fb5635a4a
When you land, things will happen in this sequence, at most Mexican airports. Some places slight variation. Mostly the same tho
1. Taxi to parking. If you need fuel, tell the tower you need "combustible" (pronounced COME-BOO-STEE-BLAY) and they will contact the fueler. Fuel truck dude is gonna keep watching soccer unless someone calls him. He will NOT go to the plane and ask if you need fuel. FYI
2. A black and white Polica Federal Preventiva (PFP) truck or car will pull up, with light-bar flashing. This is NORMAL. Airport security at all Mexican airports is under the control of PFP. Keep it friendly and say hola, and put your hand out to shake hands with the officers.
3. A 19 year old kid in green army uniform and a rifle will walk to the plane, and sheepishly ask in horrible english where you came from and where you are going. He will ask the "matricula" (tail number) and the pilot(s) names, which he will scribble down on a worn-down, rained-on, notepad. Smile and offer him a coke from the ice chest.
4. You or the handler need to physically go to the flight plan office to close your flight-plan. Bring your passports, mexican insurance with you. The airport commandante will review the documents, then stamp your flight plan form with his seal, then the flight plan office will "accept it" to be closed. Hopefully he is not on a siesta or at his latin girlfriends house. This is where using a handler, who knows Commandante Jose, is good, versus you landing and walking into his office cold. He don't know you (yet).
don't worry, no big deal