I know this is kind of late but
DIA DE LOS MUERTOS as perhaps most Americans are familiar with is mostly a Mexican tradition. If your not Mexican and so before you argue please read...many are not aware that this is Mexico's own unique celebration:
Mexico is the closest country that Americans are exposed to when it comes to this celebration and so I wanted to clear up any confusions because I see on many forums that Americans want to know more about it and end up getting info about other countries' celebration of All Saints Day and All Souls day.
The people from those countries kindly responding to the questions perhaps don't realize that theirs is not exactly the same celebration as Mexico's Dia De Los Muertos which Americans are inquiring about and most often exposed to, especially in the Southwest U.S. where it is also celebrated in many parts. I'm a U.S. born of Mexican descent from California, so I know both cultures and i will try to bridge the gap here.
I'll let others go into specifics of how its celebrated in Mexico but, in general it is
ancient and a precolombian celebration of the Aztecs dating THOUSANDS of years back, before Christianity. So you see, it is not the same as the Catholic celebration, which didnt even exsist yet.
It is much more colorful and whimsical than the Saints/Souls day others celebrate. I would say more spiritual too but then some may want to argue the point. But it is a very spiritual time, spirits are visiting, being invited back home and their presence is felt. "Dead uncle bob is coming for dinner tonight, make sure an extra plate is set and his tequila and smokes are ready for him"

(jokingly stated)
In a way it has merged with the Catholic traditions as most of the ancient ways have. I guess it was necessary to "hide" their traditions from the Spanish who "converted" the natives into Catholics. It was a ritual the Spaniards would try unsuccessfully to eradicate.The Natives had to find a way to continue celebrating their old ways. Luckily for them, there was a convenient holy day/s on the Catholic calendar that seemed similar.
Yes, Mexico being a very Catholic nation there is no way to eliminate prayers and crosses from just about anything BUT Dia De Los Muertos is mostly the ancient Aztec celebration. So in Mexico it is Dia de Los Muertos (dead children Nov. 1 and dead adults Nov 2) alongside All Saints and All Souls.
Inside the actual churches and die hard Catholics there 'probably' call it saints and souls day (since the Azted celebration would I guess be pagan) - ive never been there on those days unfortunately to see how those persons refer to it, but the majority of Mexicans are performing many Aztec rituals which I'm sure vary from region to region.
Anyhow, make sure you look for info on the right celebration whether it be one or the other so as not to get confused. Also, other south American countries may also have their native traditions on this day (i wouldnt know about the celebrations in those native cultures) but in general Mexico's Day of The Dead is Aztec/or other native tribes of Mexico and you can look up and find exactly which Aztec Gods and rituals specifically on the web.
Hope I helped. Of course then you have Halloween thrown in on the eve before to confuse even more! And yes because we are neighbors, unfortunately this is affecting Mexico's celebration. I LOVE Halloween but its unfortunte that its consumerism/marketing is affecting a spiritual day. Here at home, I will teach my baby the difference between the two (or three celebrations I guess

).
Come to Oceanside California! Our city celebrates dia de los muertos with a big city festivity to give
a small taste of what its about. This year its on Oct. 29th I'd post the link to pictures but Im a newbie here and I can post links i guess.
