While I've mentioned this before, it doesn't hurt to bring it up again: everyone here speaks English and if they don't, I would imagine that it is very difficult to function. The medium of instruction at all colleges and universities is English. It may seem unfair, but as I've explained to students who've asked me about why they have to study in English, when a country hires people of other nationalities to do their work for them, they need to communicate with the workers.
That's not to say that there aren't a lot of other languages floating around. At work, there's a constant flow of Arabic and French around me with a few smatterings of Turkish. In the break room I hear some languages from the Indian subcontinent that I can only guess at. On the street or in the shops among the shopkeepers, there are a number of Southeast Asian languages such as Filipino. On very rare occasions will I hear someone I don't know speaking Japanese. When that happens, my wife will make a new contact as was the case while out walking one day.
With all these languages floating around one thing remains the same. For lucky English-speaking monolinguals like me, the common language is English.