In a large saucepan, bring water and rice to a boil. Reduce heat; cover and simmer for 15 minutes. Remove from the heat. Let stand for 5 minutes or until rice is tender. Rinse rice with cold water and drain. Place in a large mixing bowl.
Dice the green bell pepper, red onion, and mangoes. Place in the bowl with rice. Cut cherry tomatoes in half and add to rice. Add cilantro, corn, and black beans to bowl.
Whisk together dressing ingredients in a bowl to make cumin vinaigrette. (Or add everything to a mason jar, cover and shake it up!)
Drizzle 1/2 of the dressing over the salad. Toss to combine. Add more dressing to taste.