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.