Remove shrimp from bag; discard marinade. Heat a grill pan over medium-high heat. Sprinkle shrimp with 1/8 teaspoon salt. Arrange half of shrimp in pan; grill 2 minutes on each side or until done. Remove from pan; keep warm. Repeat procedure with remaining shrimp. Toast the tortillas in grill pan, if desired. Place 2 tortillas on each of 4 plates, and divide shrimp evenly among tortillas. Divide salsa evenly among tacos, and top with queso fresco.