The orca can be found at Punta Norte on any day of the year. However, they are most commonly seen during two periods; Feburary to mid-May and mid-September to December as these are the time of the year that they are most likely going to be successful hunting either sealions or elephant seal pups.
For a Wildlife Calendar see Estancia La Ernestina who have details regarding the key species to see at Punta Norte.