According to About.com, a mango is ripe enough to eat if it gives a little bit when squeezed and if it has a fragrant aroma. A mango's color does not indicate ripeness.
Whole, ripe mangoes keep for up to five days if refrigerated. Unripe mangoes ripen if left at room temperature. Placing them in a paper bag speeds the ripening process.
Peeled, diced mango can be placed in an airtight container and stored in the refrigerator for a few days. It can also be coated with sugar and frozen for up to six months. While many markets carry mangoes all year, they are in season from May through September.