I think an important thing to think about is, do you really need an entire year to get where you want to be, language-wise? An OB I worked with over the summer spoke pretty fluent Spanish, and she learned it on a 6- or 8-week immersion program she did during her 4th year. Something like this maybe:
http://www.cachamsi.com/index.html or this
http://www.isls.com/schools/medicalspanish.php (Just what popped up on Google after a quick search, I haven't had experience with either)
The OB I worked with sounded like she exercised her Spanish pretty well since then, but she was able to handle basic exams with patients and say things like "Everything looks good!". Unless you hope to be 100% fluent to the point where you're passing the medical translator exam, then a 6 or 8 week elective might be enough for you. (BTW, some hospitals would want for you - on the record- to have passed the fluency exam when seeing Spanish speaking patients, though I see people bumble through appointments all the time without it because it can take so long for a translator to get there).