All business communications and conversations should always be conducted in a language everyone can understand. Your company is responsible for establishing a policy about which language is to be used for business conversation and communication in the workplace.
The language issue aside, any non-work-related conversations in an open floor plan are distracting, and should be kept to an absolute minimum, if conducted at all. The best way to deal with this situation is, again, for management to institute policies that clearly spell out what is and isn’t an acceptable level of conversation in the open floor plan area.
If people wish to have a discussion—either business or personal—they should move to a conference room or some other private place where they won’t bother those around them. If your company has no such policy, propose one to your manager. Better yet, if other employees feel the way you do, invite them to present the idea with you.
From the personal point of view, exclusionary conversations are also unacceptable in the workplace. A language barrier isn’t the only way to make someone feel excluded. Whenever people whisper to each other, they send out the same exclusionary message.
If two people wish to have a personal conversation, instead of whispering or conversing in another language that others don’t understand, they should move to a private place. Your coworkers are definitely pushing the bounds of considerate behavior in this regard, but you need to decide if the issue is important enough to you to say something to them.
Instead of asking them to speak English, maybe you could simply ask them to move to another area if they want to have a personal conversation, so you can concentrate on your work. This way, it’s all about being considerate—rather than becoming an issue of language.
Source: Post, Peter, "Etiquette at Work," Boston Globe