Preheat the oven to 425°F. Line a baking pan with foil or parchment paper. Poke each sweet potato 4 times with a fork and place them in the baking pan, leaving at least 1 inch of space in between. When the oven has reached temperature, place the pan of sweet potatoes in the middle of the oven. Bake for about 40 minutes, or until you can easily pierce the thickest part of each potato all the way through with a fork.(Alternatively, poke the sweet potatoes and microwave them one at a time at a time on the potato setting of your microwave. You may be able to press the Potato button and it'll start, or you may have to press the Potato button, then press Start. The potatoes can be placed directly on the microwave plate.)
Meanwhile, peel the skin off the mango and onion. Slice the lime in half, crosswise, and set aside.
Chop the mango, bell pepper and onion into ¼-inch pieces. Put them into a bowl.
Finely chop the cilantro and add it to the bowl.
Squeeze the juice from the lime into the bowl. Stir all ingredients together well.