Heat olive oil in a saucepan over medium heat; cook and stir garlic until fragrant, about 1 minute. Add onion, jalapeno pepper, and salt; cook and stir until onion is tender, 5 to 10 minutes. Add quinoa and cook until slightly browned, 1 to 2 minutes. Pour in chicken broth and bring to a boil. Reduce heat to low and simmer until broth is absorbed, 15 to 20 minutes.
Stir corn, mango, avocado, lime juice, and cilantro into quinoa mixture. Serve immediately or chill and serve cold.
