1. Heat oven to 425 degrees F. Spread tortillas onto 2 large baking sheets and coat lightly with nonstick cooking spray. Sprinkle with salt if desired. Bake at 425 degrees F for 12 minutes, flipping halfway, until lightly browned and crisp. Let cool.
2. Fill a medium-size saucepan with enough water to cover shrimp; bring to a boil. Add 2 tablespoons of the lime juice. Add shrimp and cook for 1 minute. Drain and cool slightly.
3. Chop shrimp into 1/2-inch pieces. Place in large bowl and add pineapple, tomato, remaining lime juice, jalapenos, oil, hot pepper sauce and salt. Refrigerate at least 30 minutes.To assemble:
4. Spread tostadas on one or two serving platters. Top each with a scant 1/4-cup shrimp mixture. Makes 12 tostadas.