There is a confusing thing about the post creation form - there are TWO timezone fields - one for the event time and the other for scheduling when the post will be published. I think that you were using the wrong timezone field. We need to fix that.
I did a test. While logged in as you I made a test event, with the time of it set to 11 AM Mexico City time.
Check this out, we're going to refer to it later:

That is the corresponding times in different timezones. We need those times to match with what we get.
By looking at the HTML I can see that 11AM was stored in the database as UTC:

Then when I viewed the page some javascript ran which converted the output from UTC to my local time (NZ):

Everything seems to be working as intended.

