My sister's housemate was just there and she said that it was now 2 pesos to the dollar generally.
When I was there last June (08) it was 3 pesos to the dollar.
Back when I was there it was still very cheap but the economy was going up because of the major demand for produce world-wide and the massive farmland in Ar.
I would imagine that it is still very cheap but not as cheap as Bolivia. almost 12 years ago