Where I get my haircut, a friend who works there said they are not allowed to speak Vietnamese. (As far as I know, that's the only language native to employees besides English.) I thought it was a silly rule to ban it completely, as long as they weren't intimidating customers.
There is always a problem that they might. They do makes nasty remarks about Anglo customers unless the Anglo hints that he might know some Spanish. Even then they will test your knowledge. Anglos are not the only racists.