Make sure shrimp is clean and completely dry. Combine salt, pepper, garlic, and cumin and sprinkle it over the shrimp. Add the flour to a small bowl, and dredge the shrimp through the flour to get a very light coating on it. Heat a skillet on medium high heat and add the olive oil. Once hot, add the shrimp and brown on each side, about 2 - 3 minutes per side. Remove the shrimp and let drain on a paper towel.
Combine chopped mango, onion, and tomato together in a bowl, adding a bit of salt and pepper. Assemble tacos, adding lettuce, shrimp, mango salsa, avocado, cilantro, and cheese. Spritz with lime juice.