Prep fruit and veg. Peel and dice the mangos, chop the red onion and red pepper, and chop the cilantro. Keep everything bite-sized so every taco holds a little of each flavor.
Combine. In a medium bowl, stir together mango, red onion, red pepper, lime juice, cilantro, avocado, and black beans. Add salt to taste and 1–2 tsp mango salsa or hot sauce if you want heat.
Taste and adjust. Add more lime if you want brightness, more salt for depth, or a pinch of sugar/maple if the mango needs sweet help.
Chill or serve. Chill briefly if you prefer cold tacos, or serve immediately. Warm tortillas quickly in a skillet or over a flame and fill.
That’s literally it. You made tacos.