Okay, so there's Adios Sabata which takes place during the declining days of Emperor Maximilian's reign in Mexico. I believe in The Undefeated John Wayne and Co. fight European cavalry during the period. Are there other Cinco De Mayo flicks? I'd prefer Westerns, if possible, but I'll take what I can get.

Edit: Vera Cruz is another one.
Ah, Juarez treats the story as a melodrama.
Charro! has Elvis Presley and others stealing a gold plated cannon that Maximilian used in fighting Juarez.
Two Mules for Sister Sara
Major Dundee

It isn't out yet, unfortunately, but how about this trailer for Machete

Looks dumb.

It's far too late to share with you my collection of El Santo movies, unfortunately.

Otherwise, I suggest one of the overrated Rodriguez triumverate: El Mariachi, Desperado, Once Upon a Time in Mexico.

If white guys playing Spanish-Mexican heroes is okay, then Tyrone Power in The Mark of Zorro or even the very good Antonio Banderas version The Mask of Zorro.

It's not in Mexico, but Q: The Winged Serpent refers to Aztec mythology.

You culd always get somewhat close to authentic with Apocalypto or, better yet, The Royal Hunt of the Sun about Pizarro's capture of the Inca King-God Atahualpa(?)

Holy crap! Not what I had in mind, but it would do. I guess Once A Time in Mexico could be added to this list.

For clarity's sake, are we talking about movies with plots to which the Mexican revolution commemorated on the Fifth of May pertains in some way, or are you just looking for something set in Mexico or produced by Mexicans?

Initially I was looking for #1, as I reflected I watched Adios, Sabata just a few months too early, but I expected the detour into #2, though maybe not as fast as it came. Worth it for my first look at that totally bitchin' trailer.

Holy moses, I had no idea there was more than one Sabata film! With Van Cleef and Yule Brenner trading places, no less. Must watch!

The Professionals

(Edited to add that the selection is in the right country but the wrong time period.)

The Magnificent Seven was filmed and set in Mexico, with one scene taking place during the festival of the village's founding so there's some fireworks and dancing to watch (I don't think they said it was on May 5 at all, though). Plenty of second-string characters in the movie are Mexican, and I think one or two of the Seven are half Mexican, but I might be misremembering.

Demon Island has a teens-meet-demonic-piñata during a scavenger hunt on Cinco de Mayo plotline, plus it looks like AMC is broadcasting it late tomorrow night / Friday morning. IMDB bottom 100, Nicholas Brendon, horrible CG applied to cover bad man-in-suit photography - sounds pretty painful.

Otherwise known as Piñata: Survival Island. And it's actually worse than it sounds.

The crazy thing about it is that it started out being a similar follow but with a different character (Brenner's character dresses differently, has a different gimmick rifle, etc.) called Indio Black, but when Sabata turned out to be a huge international hit, they just renamed Black Sabata and released it as a "sequel". It's probably my least favorite of the three Sabata films.

Might be the wrong revolution, but it is a great, and pretty overlooked, Western.

Pinata: Survival Island gets added to my list for next year.

Does the third compare with the insanity of the first? Sabata is probably my favorite batspit Italian western simply because of the weirdness. I'd like to see the sequels, but would prioritize a bit differently if the third is better than the second.

*Also digs around again trying to find some Sartana films*

Neither the 2nd nor 3rd are quite as batshit, but are all pretty batshit, if that answers your question at all? All three feature acrobats-2 and 3 feature ones with retarded weapons (iron hackey sacks in 2, a slingshot mounted on the guys legs in 3). 3 also has a drum with guns in it, and a clan of "Irish" men who have gold they want to protect, while 2 has an Austrian aristocrat with a model ship with cannons that actually fire, and Sabata has a gun that loads sideways, ala a Hotchkiss machine gun. Also, if you want batshit, be sure to check out Keoma, the Spaghetti Western/Musical with Franco Nero.