This is what the RAE says:
gringo, ga.
(
Etim. disc.).
1. adj. coloq. Extranjero, especialmente de habla inglesa, y en general hablante de una lengua que no sea la española. U. t. c. s.
2. adj. coloq. Dicho de una lengua:
extranjera. U. t. c. s. m.
3. adj.
Am. Mer.,
Cuba,
El Salv.,
Hond. y
Nic. estadounidense. Apl. a pers., u. t. c. s.
4. adj.
Ur. inglés (
‖ natural de Inglaterra). U. t. c. s.
5. adj.
Ur. ruso (
‖ natural de Rusia). U. t. c. s.
6. m. y f.
Bol.,
Hond.,
Nic. y
Perú. Persona rubia y de tez blanca.
7. m. coloq. Lenguaje ininteligible.
Hi everyone! Yes, the word is used in Argentina. Of course words change as time goes by. Currently, I think that the most important fact regarding the term (at least this is my feeling) is that the person does not fully "match" the environment. There is something that makes one feel that the person does not belong to a culture (of course, a foreigner does not know every single custom in another country). Perhaps, that is why in many places they use the word to refer to white people. You notice them immediately.
However, I wouldn't use this word. It's a term you may hear from people in their fifties or sixties (or even older).
Your story on the orgin made me feel curious about it, so I've done some research and found this:
http://www.snopes.com/language/stories/gringo.asp. Really interesting!