In reply to BenRoll:
Font isn't the best without a car but I guess it's doable. From the various train stations you can access a few areas with a 30-45mn walk: Rocher Canon, Restant du Long Rocher, Petit Bois, Mont d'Olivet, Mont Ussy, all of which have lots of circuits with hundres of problems from VB to V-hard. If you're keen you can also walk to Rocher Saint Germain Est (60mn walk from the station). Winter is a bit hit or miss weather wise, right now the place is being battered by gale-force winds so not much climbing happening, but when it's sunny it's paradise. Though it's good to have rest days to regrow some skin. There's not an awful lot to do in the area apart from the castle in Fontainebleau but you can always go to Paris. (Btw the campground mentioned above is nowhere near a train station and won't open until the 17th of February.)
Otherwise if you're keen on bouldering, I haven't been there but I understand you can get to Albarracín by public transport? I suggest you look it up. Might be a bit cold in winter but what do I know. Maybe look up La Pedriza, though again I've no idea about transports and weather.