Good Words and Bad Words

So yesterday we took Monica to the McDonald's Playland for lunch and every couple minutes or so she would come to our table and tell us how fast the big boys were playing. And then she tried telling us there was a b*@!^ here and there and the boys climbed on it. She said it enough times that I seriously got concerned that the boys in the playland were swearing at the girls playing. So I asked her to describe it for me and she pointed to the strap tunnel. OH! (cue lightbulb)BRIDGE!!! We, and a couple dads sitting at tables near us, laughed pretty hard. Ok, so that made sense. But she also mispronounces "ashes" when she sings "wing awound the wosie." So at what point do you start teaching that there are bad words? I'm assuming it has to be about the time they can correctly pronounce their words. Which is definitely not now. So I guess I wait? And just find the humor in it until she knows what she is saying...