the oficial lenguage for this countries are spanish
Not entirely true is it?
The most widely spoken language in Latin America is actually Portuguese, the official language of Brazil. Also we shouldn't forget that French is also spoken in Latin America and is the official language of French Guiana, Dutch is spoken in Suriname, and then we have the fun of the indigenous languages such as Quechua and Guarani, both of which are official languages of Bolivia.
So really English is the best choice, even before we look at legal reasons.
TTFN