Lay the flank steak in a large baking dish and pour the mojo over it. Wrap tightly in plastic wrap and refrigerate for 1 hour or up to 8 hours, so the flavors can sink into the meat. Don't marinate the steak for more than 8 hours though, or the fibers break down too much and the meat gets mushy.
Preheat an outdoor grill or a ridged grill pan over medium-high flame (you can also use a broiler). Brush the grates with a little oil to prevent the meat from sticking. Pull the steak out of the mojo marinade and season the steak on both sides with salt and pepper. Grill (or broil) the steak for 7 to 10 minutes per side, turning once, until medium-rare. Remove the steak to a cutting board and let it rest for 5 minutes to allow the juices to settle. Thinly slice the steak across the grain on a diagonal.
Warm the tortillas for 30 seconds on each side in a dry skillet or on the grill, until toasty and pliable.
To make the tacos, stack up 2 of the warm tortillas, lay about 4 ounces of beef down the center, and sprinkle with some lettuce, onion, and cheese. Top each taco with a spoonful of the Pico de Gallo salsa and garnish with lime wedges. Repeat with the remaining tortillas.
In a mortar and pestle or bowl, mash together the garlic, jalapeno, cilantro, salt, and pepper to make a paste. Put the paste in a glass jar or plastic container. Add the lime juice, orange juice, vinegar, and oil. Shake it up really well to combine. Use as a marinade for chicken or beef or as a table condiment.
Yield: approximately 1 1/4 cups
In a mixing bowl, combine all ingredients together. Toss thoroughly. Let it sit for 15 minutes hour to allow the flavors to marry.
Yield: 2 cups