When reading Ruben Navarrette Jr, [Send him mail] it's important to remember that he's nominally a Hispanic conservative, like Linda Chavez and Raul Lowery Contreras. His column runs on Townhall.com. Here he is writing in favor of the EEOC persecuting the Salvation Army:

So don't be surprised if many Hispanics applaud the decision by the Equal Employment Opportunity Commission to sue the Salvation Army because its thrift store in Framingham, Mass., required employees to speak only English on the job. The requirement was posted, and yet at least two Hispanic employees defiantly continued to speak Spanish while at work. The EEOC claimed that their firings violated the law. English-only proponents said the EEOC's position violated common sense.

The critics are wrong. It's not that a business doesn't have the right to expect its employees to speak English. It does. It just doesn't have the right to prevent workers from speaking languages other than English. That's what this case is about, after all – not a requirement that employees be able to speak English, but a rule that banned the speaking of other languages.[The great language debate, By Ruben Navarrette Jr., December 5, 2007]

But what Navarrette is forgetting is that employers are responsible, under another section of EEOC's rules, the EEOC sexual and national origin harassment regulations, for their employees' speech.

See Eugene Volokh's article What Speech Does "Hostile Work Environment" Harassment Law Restrict? for the gory details of what speech employers are supposed to be monitoring and preventing.

Any racial slur or sexual harassment by an employee can result in fines or liability for an employer. How is the employer supposed to protect himself from this if he can't tell what they're saying? And of course, since Mexico has lower standards of what constitutes sexual harassment or racism than Americans do, the danger that a low-level Spanish speaking employee is saying something offensive is fairly severe.