This morning I was at a restaurant and they had a Mexico/Argentina football match on. I did not pay much attention to it.
During the opening festivities, they played the national anthems. The Mexicans sang along and put their right hand (Hand extended, fingers joined) across their chest in some sort of salute. I have never seen such a thing in all my born days. Does Mexico have a civilian salute? Since when?
My wife is from Mexico (Aguascalientes) and she will invariably stand and do the salute you describe whenever the Mexican national anthem is played. Even if it is only on TV. She learned to do it in school where it was mandatory and I suppose it is similar to Americans putting their hands over their hearts during the national anthem (only with palm pointed down).
I am not sure why is that so strange in so far as a “civilian salute.” I think most Latin America countries, including the US, have a “civilian salute” to the national flag/anthem. E/a country may do it similar or different.
(You hold your right arm straight out while using your left hand to massage the vocal-cords area of your neck while roaring, producing an ululating effect.)