I'm currently learning French, German, and starting on Russian. I'm doing it all on my own though. I downloaded a learn french book and a learn german book. Found a Level 1 German workbook. Downloaded a bunch of french music and a bunch of foreign films.
The biggest help is that I downloaded this app quizlet and have a ton of french, german, and russian flashcard sets that I do when I'm waiting for anything. It's making a HUGE difference. The app speaks the words as well, so I'm learning pretty fast.
I also reached out to my friends and have a few french speakers, a few german speakers and a russian speaker that send me messages/talk to me on Facebook and so forth.
I'm learning a lot more and retaining a lot more than when I took actual Spanish classes in school.
If you aren't getting credit for it, I wouldn't take a class because being forced to learn at a certain pace will only stress you out. If you can get credit, go for it, but start learning as soon as you can because if you already have a difficult workload and you want to maintain your grades, language classes take a lot of work.