My basic french is terrible (ie non existent) but I manage to get around Paris with a phrase book and lots of smiles! It is easy to get around, and the metro system is good, though the maps are no where near as clear as the London Underground, so you may want to pick up a map and a guide book and plan a little in advance.
Instead of getting a carnet, you could get a tourist three day pass (visite), which covers you for the whole city, on the metro and all trains other than the TGV's.
Vicky