"¿Puede traer la sal, por favor?"
Translation:Can you bring the salt, please?
English, in my experience, does not use "the" in this situation, just "can or would you bring salt, please"
If you translate it to "Can you pass the salt, please," then "la" makes sense. However, even if I was asking a waiter to bring salt that was missing from the table, I would probably still say, "Can you bring some salt, please." Sometimes the use of an article or other qualifier is regional.