Preheat grill to medium-high. Brush each ear of corn with olive oil and season with salt and pepper. Place them on grill racks or mats on top of the racks, cover, and cook for 10-15 minutes, turning occasionally, until the kernels are cooked and slightly charred. Transfer to a plate to cool.
In a large mixing bowl, combine the diced mango, red onion, and jalapeno. Add the black beans and cilantro. Use a serrated knife to cut off the corn kernels from each cob and add them to the bowl. Mix together, add the lime juice and salt, and stir. Taste and adjust seasonings as needed.
Serve immediately or transfer to an airtight container to keep in the fridge for a few hours. Taste before serving, and add more lime juice, cilantro, and salt as desired.
Serve with tortilla chips, on its own, or on top of fish or tacos.
This dish tastes best with fresh sweet corn, but you can sub canned corn.
Leftovers can last up to three days in the fridge.