Like most long-term expats in France, I find myself thinking partly in French. In Paris this is no problem-- most of my non-French friends are in the same boat, speak Franglais and readily understand such phrases as "I got a PV!" [pronounced Pay VAY] or "I was flashé'd on the way to the airport"! or "She had to redoubler" or "He was the cadre in charge of ressources humaines...." or "He's doing a stage in Bordeaux."
When I come back to the States, though, it's sometimes hard to think of the right word fast enough. My mother and sister looked at me oddly when I exclaimed, "Oh, the grass has really poussée!"