The CLEP and the courses recommended here would likely duplicate in course equivalency, due to them all being equal to ie: 101,102,103. It would be near impossible to reach a level of proficiency in a foreign language that you're not already familiar with in the timeline your describing. You would need to almost 'live' it - so if you do attempt it choose a language that you have people around you that you can speak with if possible. Maybe a local library has the Rosetta Stone series to help you out prepare for the CLEP and then you could take upper level courses to reach the series needed to reach the 16 credits. It seems pretty clear that the school based meeting this requirement by students taking their foreign language each semester from the start, building up over the years. I don't think you can't do it, I just don't think your by December timeline is reasonable. If time is more important than money as far as graduating then depending on your major you may want to look at one of the Big 3.
Amberton - MSHRB
TESU - ASNSM/BSBA
TESU - ASNSM/BSBA