Side note: A couple of years ago I found myself working with a Welsh engineer who told me he learned English first as a teenager. Still almost can't believe it but he was very serious about it.
In Ireland, we have the Gaeltacht [1], which are areas where Irish is the primary language. I know a couple of older people who grew up in a Gaeltacht and only learned English in school, never using it at home. This would be much less likely nowadays, hard to avoid English on the Internet etc
[1] http://en.wikipedia.org/wiki/Gaeltacht