Just for reference, here is an Airlift bag next to a Firestone.
The mounts if I recall right can be bolted on. However, I had mine welded to the frame since I didn't want to be checking bolts all the time. You should have no problem finding people to install them even if you weld them on in Mexico, especially in Mexico City.
I would really make sure if you are going to continue on to Guatemala that the truck can take it. If you are riding on the bump stops chances are good you will destroy them. What comes after that is much more serious, possibly even a damaged frame.
Also if you lack a place to ship the parts in Mexico City. Go to a Toyota dealership, tell them what is going on and what you have to do. Make sure they know you plan to ship parts to them. I did this in Baja when my Airlift bags failed. The only problem I had was that somebody forgot to tell the guard my parts were showing up so when they showed up the guard turned them away. As a result they were sent to the mainland in route back to the USA. I caught it in time though and had them rerouted back to the dealership in Baja. Got the airbags and some how made them work for another 10,000 miles. Actually I know how I made them work for that long, tire plugs!!
Good luck!