In Seoul, I would say that quite a large amount of people can understand and speak at least a little English. In popular areas with heavy foot traffic like Hongdae, Myeongdong, itaewon and Dongdaemun you should be ok to use English because they get a lot of foreigners there. At Korea University in Anam since there are a lot of university students that had to study English back in high school and they have to take classes in English, a lot of them have a solid understanding of English but may be shy to use it. In regards to restaurants, a lot of menus have English translations so it was never difficult to order anything. I never had a huge problem living in Korea without being fluent in Korean because their English literacy was a lot higher than I had expected. Let me know if you have anymore questions if I wasn't specific enough!
In Seoul, I would say that quite a large amount of people can understand and speak at least a little English. In popular areas with heavy foot traffic like Hongdae, Myeongdong, itaewon and Dongdaemun you should be ok to use English because they get a lot of foreigners there. At Korea University in Anam since there are a lot of university students that had to study English back in high school and they have to take classes in English, a lot of them have a solid understanding of English but may be shy to use it. In regards to restaurants, a lot of menus have English translations so it was never difficult to order anything. I never had a huge problem living in Korea without being fluent in Korean because their English literacy was a lot higher than I had expected. Let me know if you have anymore questions if I wasn't specific enough!