Hi,
I just recently PCS'ed from Gunsan, South Korea which is just below the middle of the country on the Yellow Sea. First if I knew what part of Korea you are visiting that would be helpful. I'm going to go ahead and assume Seoul, Intewon (sp?) area? You will have no problem finding a place to play. Like stated above you will find mostly 4x8 carom tables, where 3c and korean 4 ball are played. But there will usually be at least one poket (pronounced poe-ket in korea)billiards club on the same street. Its quite simple to figure out which is which, look for a rack of 15 multi colored balls on the sign compared to red and white balls on the sign for carom billiards.
From my experience Koreans are very helpful if your not a rude arrogant American, they will be happy to teach you Korean 4 ball and are overall friendly people. Koreans love to gamble usually for cheap money but enough to keep it interesting, they are well versed in all the major associations rules...BCA,etc. One suggestion leave your gimmicks at home like you CTE aiming systems and crap, just go out have a good time and let your stroke fly its fun they love seeing irregular shots and chance taking.
If you have any other questions feel free to Pm me