I have since discovered that the still-green fruits are ripe when they fall off the vine. The shell never changes color, but the seeds inside go from being surrounded by a fibrous white husk to being surrounded by a clear fragrant pulp, like a pomegranate but yellow. I've been experimenting with them as flavoring in drinks. They also supposedly have a lot of magnesium and fiber. Cracking them with my teeth and swallowing them has had no ill effects that I can discern.
http://www.healwithfood.org/health-benefits/passion-fruit-seeds.php

An herbalist acquaintance was telling me how she uses the leaves to make tea, but according to this the leaves can also be used in a salad.
http://www.specialtyproduce.com/produce/Passion_Fruit_Leaves_10642.php
I'm going to try that today and see what happens.