Heat a cast iron skillet or tortilla skillet over high heat. When hot, add tortillas one at a time, toasting each side until brown spots begin to appear. Keep warmed tortillas wrapped in foil and in a 200 degree F. oven until ready to serve. Add all the marinade ingredients together in a small bowl and mix well. Pour half the marinade over the pork and marinate for 1 hour. Remove seed from avocado and cut into slices. Place a wok or heavy skillet over high heat and add 1 Tablespoon of oil When oil is hot, add pork. Cook and stir until pork just starts to brown, then remove pork to a plate. Add remaining oil to wok and add onions and tomatoes. Cook and toss until onion separates into segments. Add the marinade sauce and return the pork to the wok. Cook and stir; adjust seasonings. Serve pork, avocado and cilantro sprigs on a plate with tortillas and let everyone help themselves.
You can top these tacos with a little cheese if desired.