There were at least three around this quite large, well-planted enclosure. I found Culpeo Foxes to be reasonably common in the South American zoos I visited, with Huachipa (Lima, Peru), RioZoo (Brazil) and Santa Cruz (Bolivia) also displaying small groups.
Sorry Dibatag, I've been misleading you. These are Sechuran Foxes, a separate, smaller, species. I'd only been looking at thumbnails, and these are also known as Andean Foxes to many Peruvians. Though I'm not sure which species were on display in RioZoo, these were also displayed in Huachipa.
No, I've never seen any outside South America, and neither ISIS nor zootierliste list any. I think they make one of the most interesting fox exhibits as they are so small and often quite active (despite being typically nocturnal) that members of the public really enjoy watching them.