Carlos Pellegrini is generally in early December and was changed to the turf track at San Isidro in 1980, but traditionally, the 'sand' track at Palermo was where most of the best races were run. The Oaks and Derby (just last weekend) are run on sand, as was the Pellegrini in olden days. Both are metropolitan tracks, in the Buenos Aires metro area. There is another suburban sand track called La Plata, which is a little step down from the two biggies, but much better than the provincial tracks.
Go to
www.revistapalermo.com.ar
If you go into the section labeled Hipodromos (tracks), you will find links to the track websites.
Click on Agenda Conjunta, and you will get a calendar for when which track is running for a three-month period; 'Programmas" will get you the entries for the coming week.