I have been visiting Mexico every year for the last ten years. Mas o menos. I generally stay for 3 weeks to a month, and this year I spent a total of 3 months over two visits. Every year for the past, well, maybe not 10 years, but every year I tell myself, “I’m going to study Spanish so that next year when I come back, I’ll be able to speak it better.” And a year goes by and I haven’t studied a thing, and my Spanish is pretty much where it was the year before. I’ve even learned to tell that story in Spanish (…y todo año yo retorno y no hablo mejor el español). I generally pick up a little bit while I’m there – a word here and there, a new expression, a new verb – but mostly I’m socializing with Americans, the merchants have enough English that we all get by, and basically I have all the excuses I need.
When I ended up getting “stuck” in Mexico for the month of May while I waited on my visa to come through and a flight to become available, I decided to make good use of my time and signed up for group lessons with a private teacher. And it was great! I loved it and felt like I could accelerate in no time at all. Until I ended up having to miss a couple of classes and ultimately had to leave. 
The Mairie de Paris (Paris city hall) has a wonderful program offering continued adult education in a variety of domains, from language study to computer skills and more. You (or someone willing to go for you) have to show up (line up) at 8am on September 6 to your neighborhood mayor’s office with your form filled out and proof of residence, then validate your inscription by sending it in by mail and cross your fingers that yours gets there in time. Places are limited of course, and very much desired because the cost is minimal. Classes that normally would cost 30-50€ an hour in the private sector only come out to around 5€ an hour through this program.
Tonight I went in to the école maternelle in the Marais district where my classes will be held and took a placement test that was a lot harder than I was expecting. Although I’ll be a little embarrassed if I end up in the beginner’s class I am happy to say that this year I really am going to improve my Spanish. 
And hopefully je ne vais pas commencer hablar como este.