Mango ID and ripeness

Q: As the World's Leading Authority on Tropical Plants, I hope you can help us out. We obtained a mango tree from a City giveaway, and planted it a few years ago. This is the 1st year it has produced fruit. They are almost all green color, & range from 6-7 inches in length. Attached are a few photos of the tree & its fruit. Please help to identify the type, and how to determine when they would be ready to pick. Or should we just wait until they fall off of the tree?

A: If the tree is grafted, it normally starts flowering within a year after planting. If the tree is over 6 years old and just now started fruiting - chances are, this is a seedling (possible at giveaways) without specific variety. However the fruit looks pretty good size and shape, hopefully it tastes great. You will find out soon!
Based on the pictures, there maybe a few possible choices, including varieties (or their seedlings) Keitt, Rosigold, it can be even Lancetilla if fruit grows bigger than 7" long. The next step would be, wait until the fruit get some color, then it will be easier to narrow down the variety. Also see if there is a lot of fiber or no fiber.
You may wait until at least one fruit ripens on the tree and let it fall naturally - that will be the color (can be all green, but in your case it looks like it's turning yellow blush). After that, you may pick full size fruit before they fall and let them ripen on a kitchen table. Usually once the fruit starts showing color, it is close to ripening. For all-green varieties, just wait till fruit grows to maximum full size. You may also check if the fruit gets softer to touch, then it's ready.