The restaurant Atlantico the OP referred to has no relation to the Atlantico hotel. The restaurant now closed was run by Jaime from Portugal, friendly bloke by the way. It was (i.e. the infrastructure still is) located on the cliffs hanging over Sosua bay on the Charamicos side of town. When you get of the beach on the westside it's some 50, 60 yards to the right.
Food and atmosphere there were always superb. Too bad Jaime quit the business...