I am going to be upfront: despite being from this side of the pond, I have never been particularly good with Latin American history. I know general things and I can more than defend myself with things related to Colombian history (mainly related with 'The Violence' and Colombia's internal conflict), but when dealing with areas such as the independence or Spanish colonies I am completely lost.
With all this in mind, here comes a sort of stupid question: who is 'The Libertador'? The reason I ask is because in Colombia, Venezuela and Ecuador, Simon Bolivar is seen as the 'Libertador' of the Americas and there is a whole national myth surrounding the character and his exploits during the independence wars in all three countries. However, when you look at places such as Argentina, Peru or Chile, the tittle of Libertador is given to Jose de San Martin because of his exploits against the Spanish and his role in freeing that portion of the continent.
So... who is it?
I feel like you may have answered your own question, to some degree. There's no official authority for popular nicknames; the Libertador is whoever the person speaking is referring to when they say the name. As you said, in southern nations, they refer to a man important to that region; in the northern regions, they refer to a different man who played a similar role.
If you're not sure who someone is referring to when they use the title, rather than try and tease our their cultural background, it's probably best just to ask. Generally, in North America Simon Bolivar is the more popularly-known figure, but that's difficult to quantify. I can only substantiate the claim by saying that most American secondary history textbooks cover him in some detail, and often exclude Jose de San Martin entirely.