It depends on the situation. 你会说英语吗 means "Can you speak English?", it focuses on your language ability. Can you speak English fluently or not. 你讲英语吗 means "Do you speak English in your daily life?" or "Is English your first language?". In China, a foreigner may ask a Chinese man 你会说英语吗 so that he/she can talk with he/she in English. But he may ask another foreigner 你讲英语吗 to know whether this man comes from an English-speaking country.

Better to say “你会说英语吗 ? (Nǐ huì shuō yīngyǔ ma)”

first