Always thought this would be a really tough animal to see and regretted not joining Richard Webb when he scored in El Palmar, Argentina 2 years ago. Anyway just back from 4 days there for Geoffroys cat where we had 4 sightings of Grisons, all in groups and a crazy total of 28 animals. There’s a really helpful and knowledgeable lady in the museum / visitor centre there and she told us that grisons are very easy to see in April and May when they raid food bins in the campground.
We added 2 more Grisons in Emas national park a few days later.
El palmar is about 380km north of Buenos Aires and took us around 4 hours to drive.