Add the mango, tomato, vinegar, soy sauce, and water to a blender or food processor. Blend until smooth and set aside.
In a large bowl mix together the pork, beef, egg, breadcrumbs, garlic powder, salt, and black pepper until well combined.
Form the meat mixture into balls roughly 1 1/2-inches in diameter and set aside.
Heat 1 TBSP of the peanut oil in a large wok or saute pan over medium-high heat. When the oil is hot cook about HALF the meatballs, turning occasionally, until browned, about 5 minutes.
Transfer the browned meatballs to a plate and set aside. Add the remaining 1 TBSP of peanut oil to the now empty pan and brown the remaining meatballs.
Return all the meatballs to the pan along with the onion and bell pepper and stir to combine.
Stir the mango mixture into the pan with the meatballs and vegetables then bring to a boil.
Reduce the heat to medium and simmer, stirring occasionally, while you make the rice.
Stir together the rice and water in a medium-size saucepan and bring to a boil over medium-high heat. Place a lid on the pan and reduce the heat to low. Simmer, WITHOUT REMOVING THE LID, for 10 minutes. Turn off the heat and let sit, KEEPING THE LID ON, for 15 more minutes.
Fluff the rice and serve with the meatballs and sauce.