yes,almost every one can speak mandarin in China except rural area!
if it's real there are many people out of china interest to learn chinese,I will consider setup a website to teach chinese!haha
no boast,my mandarin is very standard,as standard as broadcaster.haha,simple because I was grew up in an oilfield headquarter where had gathered people from every province of china,local people just take a small part.So any dialect doesn't work there except mandarin.