2 weeks in Oaxaca - here's my experience.
We had rented an AirBnB for 2 weeks and have not left. We have been invited to stay for life if we choose to as I am a handy guy to have around and have not stopped working since we got here. To date I have felled a tree, repaired a car, repaired an automatic washing machine (yay - no hand wringing), installed clothes lines yada yada yada.
The skinny on the masks - I WON'T wear one and there are so many places which are fine with that. The larger stores (such as Walmart) do require, as well as handwashing. I just tell them that I washed my hands in 2019 so I'm fine.
But seriously, I will not do either - I will not validate a lie - I will not 'appease' anyone. I wore one on the plane to get here and that is it - never again.
There are many locals which mask-up, even alone in the car, but most never even look and wonder why I do not have one. There are so many little shops and street food that I just walk around all NORMAL ;)
The weather is great - not too hot, not too cold - we are on the outskirts in the hills with fantastic views and few covered faces.