If I really thought that a child was ready, I would begin dropping hints. "Wow, she doesn't like to have a wet/smelly diaper these days, huh? Good news for the potty!" I don't think I would outright say "it's time". I want mom and dad to take the lead on this one, and not just allow me to do all their dirty work for them!! It would depend a bit on the child and my relationship with the parents.