Being of a somewhat "twisted" nature, if they are insisting that the only spoken communication is in english, I'd carry a small notebook & pencil in my hip or top pocket & suggest, in english of course, to my colleagues to do the same. It's amazing how quickly a sort of text message-like shorthand develops in any language, and to anyone not involved in it's development, or the conversation, it's almost like a code.
Yes, there are benefits in terms of langauge proficiency etc to constant use, but there are ways to promote this, and it sounds like there's been little or no thought gone into this one. If the mess room's silent for a couple of weeks apart from the scribbling of pencils, they should get the message.