Many times. "Medjugorje? Conversions, conversions, conversions..."(responding to a question by Polish bishops about Medjugorje). "Protect Medjugorje" (to fr. Jozo). "If I was not the pope, I would certainly have visited Mejugorje." You can find times and places of these quotes on the internet, if you want.
Do you mean the credulity of pope John Paul II? Or of the more than 30 million pilgrims who came to Medjugorje? You do not have a very high opinion of your fellow faithful! (Also a characteristic of the Medjugorje opponents).