TO PREPARE SALSA:
Cook tomatoes, onion and bell pepper on a grill over medium high heat for 5-10 minutes or until charred. Remove from heat and place in a blender or food processor with garlic, chipotle pepper and adobo sauce. Blend or process until fairly smooth, but not pureed. Stir in cilantro, lime juice, salt and sugar; refrigerate until chilled.
TO PREAPARE BEEF:
Stir together garlic salt, chile powder and sugar. Sprinkle over beef and rub into the surface. Cook on a grill over medium heat for 10 minutes per side or until cooked to desired doneness. Let stand 5 minutes before slicing, saving any accumulated juices. Serve with salsa, reserving 1 c for Tostadas. Slice leftover beef into bite size strips and toss with reserved juices. Refrigerate until ready to use for tostadas.
TO PREPARE TOSTADAS:
Heat tostada crowns according to package directions; let cool. Place equal amounts of lettuce, beef, onion, corn, cheese, tomatoes and olives inside each crown. In a small bowl, prepare chipotle cream by stirring together sour cream and adobo sauce. Top each serving with a dollop of chipotle cream, salsa and guacamole. Serve with remaining salsa.