If they are ruby red, they are ready to be picked.

You could make tuna juice if you want, I made some two weeks ago.

Here is the juice,

Just watch out for the thorns when peeling.

I would leave them on as long as possible, given that they are safe from rodents and really extreme weather. They definitely are the sweetest when they fall off by themselves, but it is getting a bit late in the season to wait much longer...

To sample fresh you can slice one in half and spoon out the inside, wearing disposable rubber gloves usually provides enough protection from the tiny glochid spines. Only the pulpy stuff surrounding the seeds is tasty, not the tougher tissue just under the skin. The seeds are just soft enough to chew in my experience.

For processing, glochids can be filtered out with a coffee filter (I use those large commercial sized filters).

Hi Milehighgirl,
Here is what I do in the hotbed of growing cactus, the rainy and cool Pacific Northwest :),
I wait until they're red and soft and want to come off easily, like fabaceae said. Then I use two tools. I grab them off with a glove and put them in a bag. When I am ready to eat them , I grab them with the same glove, and in my other hand, I cut them in half. Then I use a melon baller, which you can get from Bed, Bath and Beyond or any store like that. I scoop out the good, sweet innards with the melon baller and eat it immediately, and throw away the skin. Easy enough!
JOhn S
PDX OR

Gee, why did I bother asking? I should have just waited for them to be stolen and then I would know they were ripe.

The skin of one was left for me as evidence that they are indeed ripe. What vermin would be willing to steal tuna full of glochids? Is there no justice in this world??? Most likely a 'coon and it will be back tonight for more.

In my orchard the hornets have been pointing me to the ripe fruits. Which reminds me, I'd better pick my Wickson apples before they are all in hornet stomachs.

Scott