Gato Dumas is a completely legitimate culinary school. I initially started taking courses at the CIA in Hyde Park, NY, but given it's price, I found that Gato Dumas was a suitable substitution.
They offer longer career-oriented courses (like the 6 month or 2 year intensive diploma program like I took) to shorter courses (sushi-making, etc). My curriculum studied basic pastries, but if I were specifically focusing on pastries, I would have taken extra classes. I also studied professional gastro, cheese/wine, pasta-making, hygiene, service, restaurant marketing/budgeting, and I learned how to de-bone quail, butchered my own javelin, made my own sausages, and even played with molecular gastronomy a bit.
Within South America, it has a great reputation. I think you'd be hard-pressed to find somewhere else with its level of detail & professional-level gastronomy at this price, anywhere in the world.
Also, it's best if your Spanish is better so that you can get the most out of the readings, etc. but can be managed without. And to endorse the competition, I know that Mausi Sebess is another fairly high-quality school but I didn't go due to the long commute. Gato Dumas is in Belgrano.