In most Hispanic countries, people answer the telephone with "Aló." Why do Mexicans say, "Bueno" when they answer the telephone?

Answer 1

In Spanish, as in English, some words are different in different countries. The "Quen's English" has different words than American English or Australian English.

Sometimes, there is no specific reason. In your example, it is true that some Latin American countries use "Alo" when they answer the telephone and the Mexicans use "Bueno". However, in Argentina "Hola" is used.

The same word could have different meanings according to the country. Sometimes, a common word in a country, could be a "bad" word in another. Example, "concha" means shell and it is use in Spain and some Latin American countries. In Argentina is a part of woman's body.

In a bus could be "la micro" or "la guagua" (if it is small) in Chile. In Argentina buses used in cities are called "colectivo" ; if they are used for transit between cities, they are called "omnibus".