Davidglen77 said:"Art. 20.- Los extranjeros gozan en el territorio de la Nación de todos los derechos civiles del ciudadano; pueden ejercer su industria, comercio y profesión; poseer bienes raíces, comprarlos y enajenarlos; navegar los ríos y costas; ejercer libremente su culto; testar y casarse conforme a las leyes. No están obligados a admitir la ciudadanía, ni a pagar contribuciones forzosas extraordinarias. Obtienen nacionalización residiendo dos años continuos en la Nación; pero la autoridad puede acortar este término a favor del que lo solicite, alegando y probando servicios a la República."
That's just the article from the constitution. So far as I understand, you have to read it in conjunction with Ley 346 and Decreto 3213/84. Bajo_cero2 is the expert though and wrote a lot about this in the other thread on the topic.
http://www1.hcdn.gov.ar/dependencias/dip/textos actualizados/346-240805.pdf
It gives several options, including being married to an Argentine or have Argentino nativo (by birth or opcion) children, that don't require two years (or any at all) residency.
I'm filing the paperwork tomorrow in the court for my citizenship after very much less than 2 years here, so we'll see how it works. The clerk in the court seemed to think it wouldn't be a problem. I have my DNI but he said it doesn't matter much. The form asks for any of CI, DNI, Passport or DNM.