Ahhh my "stay" in San Salvador. I arrived on a UA flight from LA right at dawn. My seatmate kept the window closed till the last minute so I missed the views of the volcano as we approached. The airport is just one long building. I had a 90 min. layover so I used my pidgin Spanish (don't expect everyone to speak English like in Belize) to get some food and coffee at the first food stand. I was surprised to find that you could even smoke there. I checked out the duty free shops, looked out the window at what I could see of El Salvador (beautiful place) then went to the TACA end of the terminal. There are places to buy food, snacks, water, etc after you clear their security point. Then I flew to BZE. Piece of cake.
TACA is a great airline. You should have no problems.