Bring a large pot of salted water to a boil over high heat. Add the shrimps, turn off heat and let sit for 2-3 minutes until cooked.
Remove shrimps with a slotted spoon and put in a bowl of ice water to stop it from cooking. Drain with a colander, let cool, then chop shrimp into bite-size pieces (about ½ inch).
In a large glass bowl, combine shrimp, tomatoes, cucumber, jalapeno, mango, onions, and cilantro.
In a small bowl, whisk together lemon, lime, and orange juice.
Pour the citrus mixture into the shrimp and tomato mix, season with salt and pepper, cover with a plastic wrap and let it marinate in the refrigerator for about 1 hour.
When ready to serve, add avocado and serve with tortilla chips, if desired. Enjoy your refreshing shrimp ceviche!