Mash the avocado in a medium bowl with a fork (or molcajete) until it reaches your desired consistency, chunky or smooth. Add a small squeeze each of lime and lemon juice, along with 1/4 teaspoon salt. Mix well and taste. Add more lime juice, lemon juice, and salt as you like. Stir in the remaining guacamole ingredients. (To make ahead, cover the bowl with plastic wrap and press gently against the guacamole. The entire surface of the guac should be touching and covered by the wrap, to keep air out. Then, cover the bowl with a second sheet of wrap, and refrigerate.).
prepare the black beans.
Add all of the black bean ingredients to a 2 quart sauce pot and heat over medium-low until hot. Turn off the heat and allow to cool to a very warm, eatable temp (a few minutes should do it).
If the tortillas are not soft and pliable (or if you like your tortillas warm), stack them on a microwaveable plate, separated with paper towels, and heat for 20 to 30 seconds.
Line half of each tortilla with lettuce. Spoon the black bean mixture over the lettuce (on half of the tortilla). Spoon guacamole on the other half. Top with a few shakes of hot sauce (optional) and a sprinkle of cilantro. Serve with lemon and lime wedges.