I don't pick them till I can eat them and enjoy their soft sweet deliciousness.
This could be why a lot of people net their trees, so the birds don't get them first. I can't imagine picking them sooner and hoping they will ripen, but maybe other people have a different experience.
They need to be quite soft,and often go a bit brown in places.When ripe you will find they just fall into your hand when you touch them.If they still bleed the white milky sap they are not fully ripe and you will find the texture just yuck.. and also without much flavour. But watch out for the birds, they often notice they are ripe before we do, and they are so quick!