Do I really need English captions on the photos?

Yes, if every service people ask to understand the photo in English. No, if nobody asks and the English text would go stale beside a new photo. Count in one week how many tables ask for the photo to be explained. In a neighbourhood bar everything is translated and the new photo still has a Spanish-only caption, or English with the old price. If the week asks for it, every published photo carries its English line and the same price.