I personally feel it's mandatory to know the basic "good morning/afternoon/evening - nice to meet you - thank you - please" in the primary language of the country I'm visiting, even if it's a short visit.
In Brazil, for example, is kind of alarming how little English people know (well, at least the " educated rich"), even when they have all the opportunity to learn - I guess it's what bugs me the most: many Brazilians don't make the effort to learn and speak English in Orlando, just because they realize they can get by without speaking English at all. (I haven't seen anything like this on Dis yet, but I got really tired of misconceptions/generalizations and prejudice towards Brazilians on Disney FB groups).
Long story short: I think people should make the effort to speak English, but I don't see any problems in speaking another language to the people I'm with (but if a single person in the group doesn't understand it very well, then English it is!).
PS. I HATE it when people assume I don't speak English just because I'm speaking Portuguese or German, and go on to make snarky comments. And that happens A LOT, even a CM did it once (the story: my family - as group of 5, chose to take single riders line and we were speaking Portuguese to each other - then the CM said to her colleague something like "how stupid, they don't even realize they are getting in the single riders line" - which made me boil in rage! I know I should have filed a complaint, but, you know, I wouldn't like to waste precious Disney time with someone so ignorant).