In 2000 and 2001 I did some slab/face climbing in Miryang. But I can't remember the details of how to find the place. We just parked on the side of the road and hiked up talus until we came to the bolted face. Maybe someone around there can give you better info.
You can get converters when you're in Busan. We found three-prong grounded converters in Homeplus and the Yongsan electronics market in Seoul when we first moved here.
Have fun climbing in Busan.