The area around Paris is full of parks, small towns and farms to meet up.
Paris turns out to be at the north of the graticule, so locations at the far south may be difficult to reach; on the other hand, 49 2 contains most of the northern suburbs of Paris. Ilia suggests to designate the 49 2 graticule as Paris North, and to use it whenever convenient.
For help getting to the location, use the [Parisian public transport website].
Interestingly, distances in France are measured from Notre Dame in Paris, considered the heart of the city. There's a stone saying that there ("Point 0 des routes de France"), so it must be true.
 Locations and geohashes
The GPS location for 2008-05-20 is in a farm at Moissy-Cramayel.
For similar reasons, Anap tried (successfully) for the previous day's location near the small town of Grez-sur-Loing, which turned out to be easy to find and very pleasant.
2008-07-12: In what appears to be a residential area of Leuville-sur-Orge, which is walkable from nearby RER C stations. A pair of British geohashers will attempt to reach the location by 16:00.
2009-09-23: Apparently the first successful geohash in Paris
2009-09-27: At least four geohashers from out of town are meeting up. Local Parisians are welcome!
2010-01-17: An Australian on a motorbike. Success, in the middle of a paddock.
2012-07-20: a field at the north of the graticule
 Local geohashers
Z is new to geohashing. Will be in Paris till 24 Jan 2010 and would love to try to attend this weekend's meet-up.