Defrost shrimp in fridge if frozen, remove and discard tails. Prepare an ice bath in large bowl, set aside. In a large pot, bring water with salt to a strong boil. Add shrimp and cook 1 minute or just until opaque.
Drain hot water, then add shrimp to ice bath to chill and stop cooking. Drain and chop shrimp into smaller cubes.
Place shrimp in a medium non-reactive bowl. Add lime, lemon, and tangerine juices. Stir in red onion and jalapeno. Shrimp should be submerged in liquid.
Cover and refrigerate at least 30 minutes, up to 2 hours. Stir in bell pepper and tomato. Chill additional 30 minutes to an hour.
Before serving, stir in avocado, mango and cilantro. Heat or toast corn tortillas. Using a slotted spoon, scoop shrimp ceviche (allowing liquid to drain first) into tortillas and serve.