Preheat a grill over medium-high heat and lightly oil the grates with vegetable oil. Toss the garlic, onions, poblanos and bell peppers with the olive oil, 1/2 teaspoon salt and 1/4 teaspoon pepper and spread onto a 20-inch-long piece of heavy-duty aluminum foil. Bring the 2 sides together and fold over twice to seal. Bring the ends of the foil in and up and seal. Set aside.
Stack the tortillas and wrap in a piece of heavy-duty aluminum foil. Set aside.
Toss the pieces of skirt steak with the lime juice in a medium bowl and then sprinkle with the cumin, coriander, 1 teaspoon salt and 1/2 teaspoon pepper.
Place the steak and the vegetable packet on the grill. Cook the steak, flipping once, until the meat is cooked to medium, 7 to 10 minutes depending on the thickness. Cook the vegetable packet, flipping over once, until the vegetables are soft and lightly charred, about 12 minutes.
Transfer the steak to a cutting board to rest for 5 minutes. While the steak is resting, place the tortilla packet on the grill and cook, flipping once, until just warmed and pliable, 4 to 5 minutes.
Thinly slice the steak and place on a large platter. Open the vegetable foil packet (being careful of steam), toss with the chopped cilantro and place next to the steak on the serving platter. Place the lime wedges, whole cilantro leaves, sour cream and pickled jalapenos on the side for topping the fajitas. Serve with the warm tortillas.