Combine 1/2 c cilantro, 1/2 oil, lime juice, chipotle, adobo sauce, garlic, vinegar, salt, cumin and black pepper in a large bowl.
Add steak to marinade; toss to coat. Cover bowl with plastic and chill 4-12 hours, flipping steak occasionally.
Heat 2 T oil in a large cast iron skillet over high heat until it shimmers. Remove steak (reserving 1/4 c marinade) and season with salt and black pepper; cook 5-7 minutes per side for medium rare. Transfer steak to a cutting board and let rest for 10 minutes. Slice steak against the grain.
Saute' bell peppers and onion in drippings in skillet with reserved marinade over medium high heat until crisp tender, 3-5 minutes.
Warm tortillas in a large nonstick skillet over low heat.
Divide the steak, bell pepper-onion mixture, romaine lettuce, avocado, pico de gallo and 2 T cilantro among tortillas. Fold sides of tortilla into center, then roll edge closest to you over the filling; continue rolling and tucking in filling until enclosed.