This 1971 box set from Reader's Digest has nothing to do with Mexico and everything to do with the popularity of Herb Alpert and the Tijuana Brass.
Like many of the Reader's Digest LP box sets of the 1960s and '70s, most of the selections on Tijuana: Fun with the Mexican Brass were recorded in England featuring some of the U.K.'s top arrangers, conductors and musicians.
Among the artists featured on this set is arranger and conductor Arthur Greenslade (1923-2003), a frequent contributor to Reader's Digest compilations. He often worked in films and television and served as musical director for Engelbert Humperdinck and Shirley Bassey.
Greenslade's tracks on Tijuana: Fun with the Mexican Brass included Brasilia, composed by Julius Wechter of the Baja Marimba Band and included on the group's LP Baja Marimba Band Rides Again (A&M, 1965). It was also later recorded and turned into a hit by Herb Alpert and the Tijuana Brass.
Brasilia - Arthur Greenslade & His Orchestra
From YouTube here's the original recording of Brasilia by the Baja Marimba Band.
Strangely Tijuana: Fun With the Mexican Brass was also issued in 1971 under the title Mexican Brass: Happy Hits with a Happy Beat with the same cover painting.
And the set came out again in 1974 as Tijuana: A Touch of Magic, with different cover art.
The Reader's Digest box set hasn't turned up in a digital format, although selections from it may well be included in other Reader's Digest albums on CD or via download.
Here's another selection by Arthur Greenslade from the Tijuana box set.