I found myself experimenting when someone in a Facebook group was looking for an eSIM in Mexico, but having no luck getting one from a store.

Telcel has eSIMs, but currently only for postpaid plans.
AT&T has eSIMs and does not publish any residency requirements, but the facebook poster was told by store personnel that he must be a MX citizen.
I tried the AT&T website which claims to sell eSIM, but it required ID and would not accept resident cards. Actually, it would not accept *any*.

I did find a third party ( telefoniamx.com ) which sells eSIMs for Mexico. 179 MXN for the SIM (all profit, ATTMX doesn't charge for them) and 200 for a 30 day / 4.5GB prepaid package. So far, seems to work fine.