Also, learning something online is not necessarily a shortcut, but an alternative way to learn. I'm currently living in the middle of Texas where there are no Goethe Institutes or intensive German classes that I can take. So as an alternative I am learning German by listening to online german radio and reading articles from the Sueddeutschezeitung. I'm learning all the time. I have already passed Goethe's B1 Zertifikat Deutsch Exam. Good for you if you learned German in the classroom all throughout, but that option is not always available or financially feasible for everyone.
Well, regarding taking online classes. It's a great way to start off learning a language. There are tons of programs that teach up to the B2 level of European Framework of Languages. And do check if you have a Berlitz schools nearby (they usually have them all over the world) and they have courses that go up to C2. They also have individual, custom-made courses according to the student's need (so you might want to take a medical-related course to get some exposure). Once you get a good feel for the language and take the exam, you can think of moving to Germany and taking more intensive language courses to prepare for the Test DaF (and may be even some medical courses). It's DOABLE. Just don't give up if that's what you really want to do (this is where cliches often stand true: where there's a will, there's a way )
I just met another American girl on the international forum who moved to Sweden with her husband and learnt the language there and is studying there right now. She says there are days when she meets professors she can't understand (due to their thick accent) but it still seems that she's coping up well (and turns out that most Swedes in the class couldn't understand the guy anyways).
If you intend of getting back to the US, I would really recommend that you try to get into the US and if that fails, then the Caribbean. That's the best route (and will not limit your chances of getting into a good residency program in the future).
Good luck!