In a large measuring cup, mix together the ingredients for the marinade: olive oil, lime juice, orange juice, vinegar, salt, black pepper, garlic, jalapeno, and cilantro. Mix until smooth.
Add the flank steak to the a large mixing bowl or other reusable container. Pour the marinade over it. Cover and place in the refrigerator for at least 6 hour or as long as 24 hours.
When ready to make, preheat your grill to high heat.
Remove the meat from the marinade and shake gently to remove the excess marinade.
Place on the grill and grill for 3 to 4 minutes on each side or until desired doneness using an instant read thermometer. Please note that I think this meat is best when cooked to medium rare. Remove from the grill when an instant-read meat thermometer reads 140 degrees F; let the steak rest at least 5 minutes. The temperature will raise to 145 degrees, which is medium-rare.
Serve topped with more fresh cilantro and diced jalapenos, pico de gallo, or in tacos.