I an doing Duolingo (obviously), but I am also doing a German school in Portland, Duolingo has helped me a little, and the German school you have more hands on things and you're around more people who speak German, I don't know if I should not do Doulingo, or do both.<pre>
PLEASE GIVE ADVICE!</pre>
In contexts where a certain language is spoken, it is often a fact that people try not to point out your every grammar mistake for fear of coming out as annoying. A computer-based course, on the other hand, will not be afraid to tell you when you're wrong, therefore maximizing how much of the language you become aware of. It might be a great way to hone your skills if you kept nurturing your knowledge with both methods teaching you side by side.
Duolingo would help strengthen your skills a little bit. If you want to learn German VERY quickly, you could do both. It would probably be very hard, though. I would probably stick with the German school in Portland if I were you. Good luck!
Why not do both? Duolingo only takes a few minutes of your time each day, so unless you're really very pressed for time, I don't see why you can't remain in the German school but also supplement that with a little daily practice with Duolingo.