Combine the garlic, lime juice, tequila, soy sauce, cilantro, peppers, black pepper and cumin in a resealable gallon-size plastic bag. Add the steak and let marinate in the refrigerator for 2 hours. Remove from the refrigerator and let marinate at room temperature another 30 to 45 minutes.
Preheat a grill to medium high. Remove the steak from the marinade. Put the marinade in a small saucepan and bring to a boil, then strain and reserve.
Place the steak on the grill. Cook for 4 minutes, turn 180 degrees and cook for 3 more minutes (to create crosshatch grill marks). Flip and finish cooking for 3 to 6 minutes, depending on desired doneness. Remove from the grill to a cutting board and let rest, loosely covered with foil, for 5 minutes.
Slice the steak against the grain and serve immediately with the reserved marinade.