I mentioned before on the Why Repetition is Important post, that to me getting to the point where you can do something without even thinking about it, is fluent. But this can apply to different aspects of the Japanese language.
|A good book for beginners with tips |
on speaking fluently.
I also think that what "fluency" is depends on the individual and their goals. If your goal is to be able to speak naturally then it's fine to call yourself fluent. If you want to be able to read novels but not necessarily write a lot of Japanese, that's fine too.