To get French classes, you can sign up at the universities (it is possible only for French classes, and the course is called FLE, Français Langue Étrangère). Otherwise you can look out for associations that teach French to those who just arrived and need to learn quickly.
This said, I don't know about the cost of those classes.
If you have French mates, or a job involving speaking in french everyday, you might be at ease with the language in 6 months, but if you just rely on the classes it could take years...
Hope I could help!