In a small saucepan, combine lime juice, steak sauce, the 1/4 cup salsa, oil, garlic, and pepper. Bring to boiling; reduce heat. Simmer, uncovered, for 5 minutes, stirring occasionally. Cool.
Place beef top round steak in a plastic bag set in a shallow dish. Add marinade, turning meat. Close bag securely and marinate in refrigerator 8 hours or overnight, turning occasionally.
Remove steak from marinade; discard marinade. Grill round steak on uncovered grill directly over medium* coals for 16 to 18 minutes for medium-rare doneness (145 degree F), turning once. If you like, season with salt.
Thinly slice meat across grain. Serve on warm tortillas topped with additional salsa. Makes 4 to 6 servings.
To test for medium heat, you should be able to hold your hand over the heat at the height of the food for 4 seconds before you have to pull away.
To warm tortillas, stack, and wrap in a double thickness of heavy foil. Add wrapped tortillas to the grill rack the last 6 to 8 minutes of grilling.