1. Mix lime juice, chile powder, oil, and salt in a medium bowl. Add steak, turning to coat evenly with marinade. Chill at least 30 minutes and up to 3 hours.
2. Heat grill to high (450° to 550°). Cook steak, covered, turning once, until grill marks appear and steak is slightly pink in the center, about 4 minutes. Transfer to a cutting board, tent with foil, and let rest 10 minutes, then slice thinly to fit in rolls.
3. Open rolls and sprinkle each with about 2 tbsp. cheese. Grill rolls, cut sides up and covered, until crisp and cheese starts to melt, about 1 minute.
4. Fill rolls with steak, avocado, half the jalapeños, and a drizzle of crema. Serve with remaining jalapeños on the side.
*Available at most Latino markets.
Note: Nutritional analysis is per sandwich.