Let's see: it is not worth buying designer scents for you will find them overpriced, besides the fact that offerings are limited.
Local brands might be of your interest if you are not into classics as well as high-end perfume making. Having said this...
The leader in the category is Fragancias Cannon, widely distributed in every major drugstore. Of the many brands made by them, you can try Colbert, Pino, Grandal (Canoe's smell alike) and Alliance (similar to PAco Rabane's XS).
Puig's presence is quite strong, so you will find their more popular options everywhere: among the ones difficult to find in the USA are Agua Brava, Heno de Pravia and Agua de Pravia 1905. Spanish Designer Adofo Dominguez' scents are sold in some perfume stores. AD's Vetiver is worth buying, IMHO.
They sell their own fragrance versions made by local companies (Giesso, Mancini, Karina Rabolini, Ricky Sarkani, Prototype). Most of these are easily found in major drugstores; others are only sold in specialized perfume stores (Etiqueta Negra) or in their own stores (Etiqueta Negra, La Martina saddlery, Cardón, James Smart). I have to warn you on the fact that most of these blends are contemporary in style, replicating more popular designer's blends.
Zara's fragrance waters (Sandalwood, Amber and Vetiver) are easily found in every Zara store around the city. They are good quality / good value options.
Specialized brands / "Niche"
Universo Gardens Angel has many B&M stores. Even though they specialize in aromatherapy, they sell several scents for men - http://www.universogardenangels.com/
Cabernet is made with grapes, it might be interesting to try.
Profvmvm BUE is a store specialized in personal and home fragrances. They make personal scents intended to ba layered: http://www.perfumumbue.com.ar/home.html. As far as my experience goes, their male fragrances are good quality smell-alikes. Their own version of Terre d'Hermes is called Milonga, and is quite good.
Roses are Rosres
In Paseo Alcorta Shopping Center (http://www.paseoalcorta.com.ar/shopp.../rosesareroses) you will find a store specialized in personal and home fragrances called Roses are Roses - http://rosesareroses.com/. I never tried them, so I can not tell.
Direct Marketing companies
L'Bel is a company that released several scents blended by well-known as well as not so well known French noses. They have a B&M store in Santa Fe avenue: http://tiendavirtual.ar.lbel.com/ (choose Fragancias / Masculinas /Eau de Toilette)
As JaimeB said, O Boticario's scents are worth trying: http://internet.boticario.com.br/por...te/internetbr/
Their Vetiver Brazil has good reviews here in BNotes.
Hope this information helped.