Mexico has one of the richest musical traditions in the world; to give a detailed answer is an impossible task, but I can enumerate some of the musical styles that are found in Mexico which include vocalization:
yes
During your birthday celebration.
¡SI!
Feliz Navidad
People sing songs, if they are interested in singing and they are confidence to sing.
what does Nigeria people sing
Some people sing very well, a few sing superbly, and some do not.
usually people sing their favorite songs but most people sing pop or rock songs
yes disabled people can sing all they have to do is practese
tens of thousands of people sing in rock bands
If people have the ability to zone out and sing with imense concentration as if you are happy at the oportunity to sing the song then they are able also to sing form the heart
no she does not mouth sing and she hates people who do!