If you are comfortable using the Seoul subway, I'd highly recommend the Conrad. I stayed there on points a few years ago and had an awesome stay. The paid prices can be a bit over the top though.
The property is connected to an upscale shopping center (aka mall), which connects to the subway. It is fairly well signed.

I do speak Korean (it was my job when I was in the Army), but announcements on the subway are made in Korean and English (I think perhaps others too). Most people who are about 30 or younger will know how to speak English.