Your guess is horrible. Lets take my current workplace - on my floor of about 80 people, all intelligent people who work with computers and networks, university educated, etc etc, only 2 speak fluent English. Thats about 3% - and I would consider this to be around about right.
The only reason why these 2 people speak English is because they worked in overseas branches and it was required.
Everyone else here would have studied English for a minimum of 3 years, possibly about 7 if they continued it into University, but without a reason to use English you dont remember it.