FYI, the term "hostile work environment" has a very specific meaning under the law. It doesn't matter how unpleasant the atmosphere at work may be; it isn't a hostile work environment unless the legal definition is met.
An employer absolutely may enforce an English-only rule with regards to work. It is less clear whether he may do so with regards to breaks or meal times. It certainly couldn't hurt to run your situation past an employment law attorney, the DFEH or the EEOC.
Two things I am tired of typing: 1.) A wrongful termination does not mean that you were fired for something you didn't do; it means that you were fired for a reason prohibited by law. 2.) The above answer, whatever it is, assumes that no legally binding contract or CBA expressly says otherwise. If it does, the terms of the contract apply.