Using a mortar and pestle, grind the garlic, jalapeño, cilantro, salt, and pepper into a paste. Add the paste to a large measuring cup and add the lime juice, orange juice, vinegar, and olive oil. Whisk until well combined. (Alternatively, you could add all of the ingredients for the marinade to a food processor or blender and pulse until combined.)
Spread the steak out on a rimmed baking sheet, and pour the marinade over the top of the steak. Cover tightly with plastic wrap and refrigerate for at least one hour, or up to 8 hours.
While the steak is marinating, prepare the pico de gallo by mixing all of the ingredients together in a medium bowl. Cover and refrigerate for at least 15 minutes, or until ready to serve.
When you’re ready to cook the meat, preheat a grill or broiler over medium high heat. Pull the steak out of the marinade and cook for 7-10 minutes per side, until cooked to medium (about 135-145 degrees). Place the steak on a cutting board and let rest for 5-10 minutes, then slice diagonally into thin strips.
To assemble the tacos, stack two corn tortillas together, then add steak, pico de gallo, and shredded cheese. Drizzle with lime juice if desired.