If you think of yourselves as trekkers or either walking expert, getting to the Fata Morgana Fountain will be a nice, challenging experience, being most of the path a continous uphill which spread itself around Florence hills. The last part of the country path becomes at last a downhill, leading right to the beautiful Fountain.
I also understand that many of you are not such impavidous trekkers. Therefore, here's the better way to get to the Fountain:
first of all, I recommend renting a car, because in any case this place can be reached though a main road that connects Florence to the borough of Bagno a Ripoli.
By bus: from the train station, take bus # 31 or # 32, and ask the driver to get you off at bus stop FORTINI 11.