It depends on which side of the world you're talking about.
In China alone, there's more than 1.5 billion
fluent mandarin speakers. (1 from 5 people can speak fluently mandarin)
Also, wherever you go in Asia, from traffic signs to front desks,you can freely read chinese characters/also talk with staffs in the "universal language".
In Japan again, half of my scholarship classmates were chinese.
Ok, let's talk about here,the Occident.
I use so much more mandarin on my daily-basis than english, and that's not because I live in a "Chinatown" here in São Paulo.
Simply wherever you go to shop, eat, there will be a lot of chinese.
Liberdade,25 de Março,Brás..from gadgets to clothes,kitchen tools,whatever you want to get a discount.
Indeed it's a very useful language when you're going down to business.
Moreover,in today's world,any big and cosmopolitan city you visit, there's a Chinatown.
You know, many americans today learns chinese,the language of the future
Below, some links to help illustrating my speech.