When do people sing las mañanitas in mexico?

in the morning
late at night
in the party after a wedding
only if they are mariachis
at every birthday

At every birthday

Explanation:

Mexicans usually sing las “mañanitas” at every birthday, especially right before blowing off the candles of the cake. It is basically the Mexican version of the “Happy birthday to you” song, although the lyrics are more elaborate, for they refer to the day that someone was born in a folkloric way.

Sometimes, but not all the times, this song can be part or the repertoire of a the mariachis, if they were hired to a birthday celebration or a serenade celebrating someone's birthday, however mariachis have a great list of songs. On the other hand, anybody could sing Mañanitas song, and not only mariachis.

Also, it is not aproppriate to sing the Mañanitas song in the party after a wedding unless it is somebody's birthday, for the celebration of the wedding is marriage and not that someone was born.

Finally, the Mañanitas song can be sung at any moment of the day: in the morning, late in the night, or in the afternoon, no restrictions are made for this matter, because it can be freely sung at any moment of the day.