Mr. Loco is a fairly obscure Mexican band, but Beck knew of them and introduced them to the Nacho Libre people. (Beck had actually sampled Mr. Loco's song "Bubble Gum" on "Hotwax" way back in 1996 on Odelay.) In return, Mr. Loco on the 1996 Nacho Libre soundtrack, next to some of Beck's score.
One of the Mr. Loco songs on the soundtrack is a jaunty little track called "Religious Man (Hombre Religioso)," the lyrics of which are below. It can be found on their 1975 album, Lucky Man, and is also the opening track on the Nacho Libre cd.
Interestingly, Beck contributed a re-write of one of this song to the soundtrack. However, it is not available on the CD, but Beck's version leaked somehow (I forget how exactly; but you can hear it below).
Over a fluid bassline and some sort of flute-like instrument, this is a very pleasant song and features briefly in the film. I like the grandiosity of some of the lyrics ("see the flower open to the sky / see the eagle learning to fly"), which fit the silliness of the film.