In reply to JLDyer:
I don't drive and have had a few good trips to Font:
- Staying in Paris and getting the train to Bois le Roi and waking to Rocher Canon, or to Fontainebleau and walking to Mont Ussy
- Staying in Fontainebleau and cycling to Franchard, Apremont, Canche, St Germain, 95.2
- Staying near Camping La Musardiere and cycling to loads of areas in Trois Pignons
Buses are pretty rare and probably not much use, taxis would of course get you anywhere.
If it was going to be walking only, Trois Pignons might be your best bet