Back in January I visited "Coreanos Kitchen" - a Mexican-fusion restaurant in Apgujeong/Rodeo. According to the waiter, they opened in September 2013, and it seems like they're doing great! Celebrities seem to visit fairly often, and throughout the hour and a half I was there, there was a good crowd of people.
They have a happy hour there from 5-7 from Tuesdays through Thursdays, and drinks are 50% off. The rest of their menu is quite affordable as well, so if you're looking for a great place to watch a game (flatscreen TV was on ESPN the entire time we were there!) or hang out with friends, Coreanos is the place to be.
We pretty much ordered a bit of everything: a quesedilla, burrito, tacos, fries - and then finished out the night with dessert (... like you're surprised?)
Overall, the meal was extremely enjoyable. They have other menu options like guacamole and chips, and tostadas and tortadas. I'm sure I'll be visiting again soon to try those dishes.
To make your way to Coreanos Kitchen, go to Apgujeong Rodeo Station (Bundang Line), and come out of exit 5. Go straight and take your first right. Go straight about 200 meters, and you will see Coreanos on your left. Go downstairs to find Coreanos Kitchen in the basement.