Its hard to tell from the photo. They don't look ripe to me.You really have to wait until they are, at the soonest, about 2 weeks from ripenning on the tree to pick them prior to ripenning. If you pick them too soon they will not ripen. If you arent afraid a critter will get them, then let them ripen more and get some color if they are a variety that gets color (most do)and they may get a little soft to the touch. check out this website www.tropicalfruitnursery.com. They have a mango variety info site. It may help. Most mangos are over with in S. FL except for Keitt and Kent varieties. The ones in the pic are not those.
rusty

Most var of mangos ripen later in Ca because they bloom later and develop slower since summer nights are cooler that Florida..

I read that mangos ripen in Nov or later in California..

Thank you for the advice.

I bought Mango plant from Home Depot and it was labeled as "Manilla mango" which is a yellow mango often available at supermarkets here. The fruits I have seem larger than the Manilla mango I have seen in supermarkets. I guess i will cut on fruit and keep it in a dark warm area to see if it will ripen and keep the other on the trees until it is really cold here.

Your right, the fruits seem different than a Manilla, it seems rounder. I have heard that many of the manillas are propagated through seedlings because of its polyembryonic nature. It could be a variation due to that. Was there any graft lines on your plant?

Eggo:

You are probably correct. There is non graft union on the Mango tree. So, it is likely grown from the seed. The one mango I harvested turned yellow and soft and tasted and smelled (or lack of) just like the Manilla mango.