Ok, where to begin...I deferred matriculation for the 2003-2004 school year so that I could teach English in Japan so I understand what you are looking forward to doing. Here is my advice...in no particular order.
1) I have found that contrary to what other posters have said, MANY medical schools are very willing to let you defer your enrollment for *1* year. (I did notice that state schools may be less willing to hand out deferrals though...however, in my state, the school I was accepted to had no issues). Whether or not the deferral is granted though all depends on the discretion of the school. Usually if they are to grant the deferral they want to see that the year will be used for constructive means (eg a year-long Grand Tour of Europe to "find yourself" probably won't cut the mustard).
2) To see if a school is willing to grant a deferral contact them anonymously (phone call!) and ask what their policy is re: deferrals. If you ask at the interview then it can sort of make you look like your med school apps are a sort of fall back plan. (Why should a school make the effort to accept you if they KNOW you are going to defer? They are going to give that seat to someone they KNOW will be there occupying a seat on day 1) I only brought up deferral and my name together in the same sentence once I had been accepted.
3) When you do ask for a deferral, make sure that you DE-emphasize your personal gains and emphasize how your deferral will be able to make you a better physician. (I talked of how living in working in a different culture would make me more sensitive and understanding when working with immigrant/foreign patients and that it would be a way for me to understand how Japanese and to a lesser extent other East Asian cultures deal with medicine and their own culture...I didn't say I got a great paycheck, an opportunity to travel, and a year to recover from senioritis at my college).
4) If the school's you are interested in will let you defer I highly recommend applying this year. Applying from Korea is bound to be a nightmare (with travel and such) and waiting to apply the year after that is just setting your life back WAY to far, in my opinion. Also, some schools only will use MCAT scores that are within the last 3 years (although I would say most will use scores from up to 5 years ago...again worth checking with the individual schools)
5) The ONLY sticky point! When I was asking about the deferral, they made it quite clear that UNDER NO CIRCUMSTANCES was I allowed to be enrolled concurrently at another college/university for the duration of the deferral. I am not sure if this is specific to my medical school or if it is an AAMC rule. Also, I was treated like a matriculating student up until orientation stuff came out, so I had to submit a final transcript, yadda yadda. Med schools in general won't accept students who won't have a diploma in hand the summer before they begin school, so I am doubtful that they will let you defer if you haven't graduated, but again, check with the school.
6) I would say also, maybe it would be easier to find some sort of job in Korea or volunteer work where you could definitely improve your Korean but also help others as well so as to get around the stickiness of being enrolled in a university. I am on a salary, but that didn't seem to bother anyone when I was asking for a deferral...they heard "teaching English" and "Japan" and thought it was very humanitarian sounding.
7) I applied for med school and the program I am in Japan at the same time...sort of the one hand doesn't know what the other is doing approach. Not sure if your uni program would care that you are applying to med schools but just thought I would throw that in there. Anyways, what I guess I am trying to say is, I don't know how much time you'll have between when you get accepted into your Korea program and when May 15 rolls around. For me, I didn't know I was accepted into the Japan program until mid April which meant I had to get a really quick turnaround for the deferral granting. I had to write a letter requesting the deferral and then that had to go before the committee on admissions and they had to discuss yadda yadda yadda. One of my schools was great and granted my deferral in a week, and the other one, well when May 15 rolled around they still hadn't made a decision (even though they said there was a good chance it would be granted they also said that they were still reviewing applications and waitlist issues and deferral granting was not high on the list of priorites). When it got down to it, I let the deferral choose my medical school...which I was relieved about anyway because I was torn between 2 awesome schools and I just couldn't decide. (NB Hold on to ALL acceptances until you have the deferral from your #1 choice)
7) LAST THING. You *will* have to resubmit AMCAS if you defer. It is a giant PAIN IN THE ASS as your med school knows you are coming, they are cool with you being deferred, but to keep their paperwork in order AMCAS makes you reapply--maybe resubmit is a better word-- (luckily you don't have to pay anything) and you have to update all of your personal information, type any grades from your 2nd semester of sr. year and all of that crap. You also have to get your university to send another transcript to AMCAS. With Japan/Korea and America 11-14 hours time difference it can be a pain contacting them, and I don't know about your college, but for mine, fax and snail mail are the ONLY ways to request a transcript, and our registrar is notorious for needing to be prodded to make sure your transcripts get sent out.
Even though it may seem really complicated, it isn't that much extra work. If you get your deferral it makes your life a whole LOT easier, and I highly recommend, if your plans allow it, for you to go for it.
If you have any other questions, please post them and I will try to help you out!
-dcpremed