Avi, you might want to try the session held at 22.00 (ish) every Thursday at "The Blue Sly", Rue Delambre, Metro Vavin or Edgard Quinet. It came highly recommended to me by a friend and music partner of Robin Bullock's.
I was in Paris in February, and though I wanted to, there wasn't a session to be found. I spent 6 nights there, but Thursday wasn't one of them. I tried some others listed on Thesession.org, and to no avail. Connelley's Corner, which came highly recommended, was closed for an indeterminate amount of time. Several other places I had called or asked about didn't have a session.
I highly recommend the Cite de Musee (Music museum). It's the most amazing collection of historically significant musical instruments I've ever seen in one place, including in books. I dare say that most of the really great books on the history of musical instruments features photographs of instruments on display in their collection. There is a wonderful John Lennon retrospective at the museum right now. If you will pick up a couple of John Lennon posters from the museum and ship them to me, I will be forever in your debt and will compensate you handsomely for your effort. Mine was destroyed going through baggage handling and I have no way to get another. Even one would be enough, but if I could order them from the museum, I'd probably get a half dozen or so.
Rosine and Francois Charle's instrument store is quite pleasant, but if you don't speak French, you're better off being there when Francois is available--toward the end of the week. I was fortunate that a customer was willing to translate between Rosine and I. The store is hard to find, as it is in a gallery that is off of a short street that is not named on the free tourist maps. You need someone to give you directions or a really detailed map to find the store based solely on the address.
If you're into museums, skip Louvre and go straight to Musee D'Orsay.
I could probably keep babbling like this, but I don't know what your interests are. I spent a week just walking around with my camera. It was a terrific experience! I shot more than 300 "keepers" and a handful of truly stellar photos, even given the damp weather I encountered. People were warm, even though I didn't know how to say much more than "I'm sorry, thank you, hello, and I don't speak French".
I hope this helps!
"I'm not buying a banjo, I'm performing a public service by taking it off the market"