Absolutely let it mature and eat it, If you have fruit flies in the area protect it by bagging it in some fashion.

I have and have had many guava and allowing them to keep their fruit does not affect their future health.

SOME guava will give off a VERY aromatic scent indicating it is time to harvest, others you have to go by color. Some stay firm and others get soft when ripe. You have to be familiar with the one you own to eventually know more.

Let it grow. My tree started off with about 7 fruits. Then the next time it fruited there was 15 fruits, then 30 fruits. Now it has over 100 fruits at one time.

Okay, then I'll let it go then and let it reuse the energy for a bigger crop next year (it's a small tree though so we'll see)!

Which month is typically the best time to harvest, or how can you tell when a guava fruit in ready to harvest?

Guavas are ready to be picked when they soften and change the colour......they also have a strong smell when are ripe