The Mexican living environment.

The biggest change one has to accept in Mexico, is that Mexicans live together in much less space than American citizens do as a general rule.     That will be hard for many people to get used to.

So what is different here?

Well , most Mexicans work 6 days a week so you are unlikely to see the usual weekend.
Most women wear high heels and skirts instead of shorts, but that is changing.

The people are very polite for the most part, and they usually greet others.
They are quick to help, or give directions.

You do have to be selective about who you get your directions from though. I tend to stick with taxistas, and well established businesses. It's not that they are misleading you, it's that they want to help so they will direct you to be helpful. Sometimes that is not so helpful at all.They mean well but may not know exactly where it is.

True, A Mexican would rather give you wrong directions than admit he doesn't know.  Overall, they're very helpful.

I agree with other posters that respect is key. If you can't or won't give it, don't come here. Seriously. You'll be miserable and we will all despise you.

Don't wear your mood on your face, unless it's a good one. Very uncool to have an attitude while walking around -- and keep your disagreements & fights with your spouse, friend, kid etc in PRIVATE. No bickering out in public

Walking is challenging if you're not fit or have physical impairments. Lots of cobblestone streets & sidewalks that are narrow and often broken or blocked. I absolutely love walking here and do it every day, but I know I'm just one accident, injury or illness away from not being ambulatory in Mexico.

I get bottled water and use it for EVERYTHING except for showering or washing dishes.

I think you must be reasonably physically fit to live here. Of course, you can always take a taxi or Uber. Very inexpensive. THAT SAID... Mexico is a land of many stairs and narrow entry ways. Any idea you have about "ADA friendly" -- forget about it here. Point being:  if you have physical problems that keep you from easily and regularly navigating lots of stairs and narrow passageways-- don't come to Mexico

I absolutely love this country. But it is not, nor will it ever or should be, an economy version of The U.S. My best advice is to be really honest with yourself. If you're not really open to new experiences, different ways of doing almost everything, being humble & respectful to th ways of others, and most importantly -- if you're not someone who deals well (and embraces) profound change, then don't come to Mexico. It doesn't make you a bad person. Not everyone is cut out to be an adventurer. But if you are, and you really believe you could make a new life for yourself...then c'mon down! Mexico is an amazing place.