What I mean is, my two year old knows two words for lots of things, but I don't suppose he really has any idea why everything has two words. At what age do you think you should start teaching that one set of words can be grouped as "English" and the other as "Spanish"? I've been tempted to say "say it in English" when he speaks Spanish to me, but then I realise he doesn't really know what that means yet. At the moment it's more like he says it in Spanish, I repeat in English, then he repeats in English.