There are several Mexican Health Insurance Programs available to ex-pats. Most have a maximum age limit for which they can be obtained, and several will terminate at a given age. All have pre-existing limitations. Many plans are accepted by the private hospitals in Mexico, especially the larger ones.
Plans differ widely. In order to determine the best Mexican plan it is best to contact an agent, who can provide a wide range of programs for you.
There is one Mexican private program for those over 60, called Plenitus Senior, described in the Senior Insurance page. This is currently available only through the representing agent, Hector Lavin Rios at firstname.lastname@example.org, (55)5677 4933