This is another "tradition" that I need to expose as being bull shit. It's just like New Orleans Voodoo, so much so that it's rather scary. Just as New Orleans Voodoo is bull shit and is nothing but mutant hoodoo, "Mexican Santeria/Voodoo" is mutant Mexican folk magic that practitioners try to turn into a religion and claim it as being Santeria or Voodoo.
When I say Mexican I mean Mexican. These practitioners are normally Mexican and either live in Mexico or they have immigrated to the U.S. They are just like New Orleans Voodoo in that there are people within this practice who call themselves priests and priestesses, even though they have never been initiated by a genuine priest in either Santeria or Voodoo. Like with New Orleans Voodoo, these people will happily perform, for pay, any of the services that a genuine priest would perform and they hold dances and ceremonies which attempt to mimic the actual services of the two religions.
Legitimate Santeria is well known to be heavy in places such as Cuba, Puerto Rico, and in New York City and near Miami, FL. Legitimate Voodoo is found in Africa and Haiti but can be found in Florida as well. Mexico is not really known for being a center of Santeria or Voodoo.
Like with New Orleans Voodoo, it is possible to tell Mexican Santeria/Voodoo from legitimate Santeria and Voodoo by a variety of things. Most "priests" in New Orleans Voodoo and in Mexican Santeria/Voodoo, will dress up almost like drag queens. Their dress is over the top and heavily theatrical and does not match the dress of legitimate priests. There dancing is absurd and is nowhere near the traditional dances of Voodoo or Santeria. The rituals and ceremonies tend to have a "Wicca" like-feel to them with regard to how the deities are addressed. Also, they may mix and match deities. One of the things that gives New Orleans Voodoo away is that they freely work with deities not only from Voodoo, but also from Santeria and even pagan gods. A similar thing will happen with Mexican Santeria/Voodoo, where they will incorporate all kinds of spirits and claim this is part of their tradition.
So, if you see a group of Mexican people who claim to be Santeria or Voodoo then I would be a bit cautious. Check them out to see if you notice any more warning signs that they are of the fake "Mexican Santeria/Voodoo" instead of the legitimate practices.