Everyone in Korea uses a GPS. Even bicyclists. One or two can be found there that are somewhat bi-lingual but if you can learn at least the Korean alphabet you can probably work a Korean one without too much trouble. Street maps can be found for certain Garmin devices. There is also the Open Street Maps project. And yes, the bread trail and dead reckoning value is there even if you can't read the thing.
Most Korean GPS receivers come with warnings of speed cameras. Nice thing about motorcycles is that the speed cameras take pics from the front, so motorcycles can ignore most of those warnings.
You can also park nearly anywhere. Unlike cars, where parking is quite effectively controlled by cameras.
If you stand around looking lost long enough, someone with [variably] basic English skills will try to help soon enough. Most Koreans are very friendly and especially if you're in an unusual area for tourists or service men, curious to know why you came. Best luck is with business men, men old enough to have been adults during the Korean war, and young kids trying out there school-taught skills.
Another good reason to learn Hangeul is you have a better chance of pronouncing things correctly, which seems unusually crucial in Korea. If you try to pronounce the name of a place the way it looks in the transliteration on a road sign, most Koreans will just stare at you as they ponder what you were really trying to say.
Easiest way to impress any Korean at all is to be able to say a few basic things in Korean. HUGE additional brownie points if you get the honorifics right when speaking to elders or superiors.
Most cops there speak little if any English. This can be bad if you're in a pickle or lost. It can be good if you just broke fourteen traffic laws, because it will be too time consuming and awkward for them to bother with you. Though that is my experience as a civilian. Not sure if they will treat service men better or worse. I wonder if they may hold you to a higher standard if they see a high 'n tight when the lid comes off.
New Yorkers: Join the NYMSTF now for a motorcycle -friendly NY!