To make the quesadillas, heat a large nonstick skillet or electric griddle over medium-low heat. Add a bit of cheese on the bottom of each tortilla, then divide the shrimp evenly between the two. Cover with the mango, tomatoes, onions and remaining cheese, then top with the other tortillas. Cook until the cheese is melted and the sides of the tortillas are crispy. Serve with the guacamole, sour cream or greek yogurt and extra mango.