Mexicans answer the phone with the word "bueno". The reason is historical. Telephones were installed during the time of the Mexican revolution (1910-1923). Lines were frequently cut as a result of the wars between the various factions. Bueno means that the person answering hears that there is a good connection.

In South America, many phones were installed by the Swedish Erikson Company, and the French word "Halo (Aló) was used. This is used by many Spaniards as well.

In the Caribbean, they normally answer with Diga (speak) or Digame (talk to me) or Oigo (I hear). This is used by many Spaniards as well. Some answer the phone with the word “Si?” ( Yes?)

In the beginning – Alexander Bell thought that people should answer the telephonewith the word, “Ahoy.”

Edison proposed the greeting of “hello.” The word was consider to be more efficient than alternatives such as “Are you there?” or “Are you ready to talk?” Edison proposed the word in an unpublished letter dated Aug. 15, 1877, addressed to Mr. David, president of the Central District and Printing Telegraph Company. Mr. David was preparing to introduce the telephone to that city.

Edison addressed the issue as follows: Friend David, I don't think we shall need a call bell as Hello! can be heard 10 to 20 feet away. What do you think? EDISON

At the time, the word hello was not a greeting. It was a call used by hunters. The word was the traditional call to incite hounds to the chase, and is a close relative of such words as hilla, hillo, halloa and hallo, words which were all used to hail or greet people from a distance.

Hello became the standard as the first telephone exchanges, equipped by Edison, were set up across the United States and operating manuals adopted the word. The first public exchange, opened in New Haven on Jan. 28, 1878, listed both "hello" and "What is wanted?" in its manual. By 1880, "hello" had won out

http://www.nytimes.com/1992/03/05/garden/great-hello-mystery-is-solved.htmlhttp://www.repairlabs.com/worldwide-phone-etiquette