Place the meat or chicken in a Ziploc bag with the lime juice, garlic, and spices, and marinate in the refrigerator for at least 45 minutes and up to 5 hours.
Heat the oil in a skillet or wok, and cook the peppers with the onions until soft, stirring often and adding salt and pepper as needed. Set aside and keep warm.
Discard the marinade. Add one tablespoon of oil to the same pan and stir-fry the meat or chicken strips until done (about 5 to 8 minutes), again adding salt as needed.
Spoon the cooked meat and vegetables into the center of the lettuce leaves. Add a slice of avocado or some guacamole. Fold or wrap the lettuce around the filling and if you like, secure with a toothpick or tie with blanched chives.
You can serve alone, or with sides of salsa and guacamole.