Regarding rates, I don't know, but I would say during the winter; it gets nice and cold. My suggestions would be the world heritage sites:
Cave of the Hands (Cueva de las Manos), Río Pinturas. Has prehistoric cave paintings (WHS since 1999).
Iguazú National Park, home of Iguassu Falls (1984).
Ischigualasto / Talampaya Natural Parks and its paleontologic formations (2000).
Jesuit Block (Manzana Jesuítica) and Estancias of Córdoba in Córdoba Province (Cultural Heritage) (2000).
Jesuit missions of the Guaranis: San Ignacio Mini, Santa Ana, Nuestra Señora de Loreto and Santa Maria Mayor (1984).
Los Glaciares National Park and the Perito Moreno Glacier (1981).
Península Valdés, a marine wildlife preserve (1999).
Quebrada de Humahuaca, World Cultural Landscape for its scenic natural beauty and historical sights (2003).
or anywhere where there's nice hotels like Córdoba, Buenos Aires, or Mar del Plata. Argentina is a very beautiful country.