Soak 4 bamboo skewers in water for 30 minutes. In 1-quart resealable food storage plastic bag, combine cilantro, garlic, margarita mix and tequila. Add shrimp; seal bag and shake to coat. Refrigerate 30 minutes to marinate.
Meanwhile, heat grill.
When ready to grill, thread shrimp on skewers; discard marinade. Place shrimp on gas grill over medium heat or on charcoal grill 4 to 6 inches over medium coals. Cook 5 to 7 minutes or until shrimp turn pink, turning several times.