The deokpo driving school didnt have an English instructor last time I checked (maybe 3-4 months ago). Last guy retired and they never replaced him, although thats not to say they have one now).
There is one in Gohyeong, but its a bit complicated for directions to get to. They definetly have an English speaking instructor, and the guy at reception speaks a bit of English as well, he can take you through the application process (think it costs around 1million in total).
If you need anymore info, contact me throught the firstname.lastname@example.org email address.