Mexican here. Generally, most of the population won't be very welcoming. Talking specifically about mexico city. You see, the amount of money you make in tech in the US will allow you to stay at the very best places in the city, which pushes native people out of those districts and makes them angry in the process. However, those districts are already popular for tourists/rich immigrants and that's probably for a reason. I guess business there benefit from this wealth availability so they will treat you well. I'm not rich so idk. Also, it's probably not hard to emigrate here bureaucracy wise.
Speaking Spanish, you will likely do very well in mexico. Good food, good nightlife, good safety and infrastructure (assuming you stay in the good zones), etc.
Personally, having traveled to other countries (talking about US and places in Europe specifically), I love the diversity of nationalities you can find. I think different backgrounds and experiences is very important to drive innovation. I'd love to see more of that in my home country so I'm for more people emigrating to mexico. Feel free to ask questions if you are curious.
Well, yes of course. Some relatives have few foreigner coworkers and they seem to be happy. (tho I don't know them personally). Also I've met some foreigners through university and they seem to adapt well. But I guess it heavily depends on what kind of lifestyle you want to have.
People are usually warm and we appreciate it if you show interest in our culture and adapting here. You should be more than fine if you are mindful to that and better still if you are naturally outgoing. Good luck and hope you find a cool place to go, or things get better if you end up not moving.