[West Ender]

I really don't think it matters if non-natives speak in their own language to each other. What is important is that they should be able to speak and understand enough English to be able to go shopping, go to hospital/doctor's surgery, go to a government department etc. It's basic common sense to realise that this is in their own interest as well as that of others. It's not easy to do at first, when you've grown up without learning English, but practise makes perfect.