Based on the level of respect or formality, you can say "Do you speak English?" in Korean in 3 ways:

• Informal: neo-neun yeong-eo-reul mal-hal su itni? (너는 영어를 말할 수 있니?), neo-neun yeong-eo-reul mal-hal itseo? (너는 영어를 말할 수 있어?), yeong-eo hal su itni? (영어 할 수 있니?) - neo-neun can be omitted
• Formal: dangsin-eun yeong-eo-reul mal-hal su itnayo? (당신은 영어를 말할 수 있나요?), dangsin-eun yeong-eo-reul mal-hal itseupnigga? (당신은 영어를 말할 수 있습니까?) - dangsin-eun can be omitted
• Very Formal: dansin-ggeseo-neun yeong-eo-reul malmasseum-hal su itseusipnigga? (당신은 영어를 말할 수 있으십니까?) - dansin-ggeseo-neun can be omitted

- you (subjective): neo (너), neo-neun (너는), dangsin-eun (당신은), dansin-ggeseo-neun (당신께서는)
- to speak: malhada (말하다)
- Korean: yeong-eo (영어)
- language: eo (어), eoneo (언어)

Please refer to How to pronounce Korean Alphabet for the English pronunciation in this answer.