Hi Laura, I have a couple of papaya trees also. I think you have to wait till you see a little bit of color (yellows/reds) depending on variety on the skin. Once you see some color on at least 1/3 of the plant's skin, you can pick it and let it ripen on your counter or pantry. Also they will soften a little to touch, similar to Mango... If you pick it too soon(too green) it will not ripen and probably start to rot. At least this has been my experience with mine. Enjoy! Here is a link that might be useful:

It will change color & come off with a slight tug. Don't pick it early! Just leave it on there & if you forget, it will fall off- But that's fine. I had one fall & I thought I lost it.. Was rather angry as it was a cross... But I found it again 3 weeks later & it was fine.

Check out this photo. The darker red ones at the top of the cluster are ready to eat. The orange one in the middle of the cluster could be eaten but would be better if given another day. But in truth you can pick them at any time once they begin to show any color and just let them ripen on the kitchen counter out of direct sunlight. Dave Here is a link that might be useful: Sweet 100 tomatoes

What size is your guava? Some are eaten harder and crunchier, while others are used primarily for juicing and tend to ripen to be much softer. And as aroideana says, guavas when ripe are very fragrant. pungent. Personally I find it to be more overpowering than durian, but I might be the only one.