Rub both sides of sirloin patties with barbecue rub.
Place patties on grill over medium-hot coals (350 to 400); grill, covered, 6 minutes on each side or until done.
While meat cooks, combine mayonnaise, salsa, and bacon bits.
Place lettuce leaves on bottom halves of buns; place patties on lettuce. Top with onion, tomato, 2 tablespoons mayonnaise mixture, and remaining bun halves.