In medium bowl, combine shrimp, taco seasoning mix, garlic and 2 tablespoons of the lime juice; toss to coat.
Heat oil in large skillet over medium-high heat until hot. Add shrimp mixture; cook and stir 2 to 4 minutes or until shrimp turn pink. Remove shrimp from skillet; place on plate. Cook remaining juices in skillet for 3 to 4 minutes or until thickened, stirring occasionally. Return shrimp to skillet; stir to coat. Remove from heat.
In small bowl, toss avocado with remaining tablespoon lime juice. Spoon shrimp mixture into taco shells. Top each with lettuce, avocado and tomato. Serve with salsa.