Assuming you're playing in a country where English is the main spoken language then yes, this is typically a rule for live games, particularly in
casinos. In other countries it's common for the native language AND English to be allowed (pretty sure this is the case at the
wsop events in France, for example)
Exactly how rigorously the rule is
enforced is another question though. It might be enforced in a major televised tournament, but other games are a different question.
As someone who just plays regular low-stakes cash games I've come across many situations where players have been speaking in other languages to each other (and, memorably in one spot, a dealer speaking to a player in Mandarin) but I've never seen anyone be penalised, or even seen any other players speak up about it.