Pay for welders in Mexico right now
From what I've seen in the last couple years, welders can pull in decent money depending on the city and the type of work. In places like Monterrey or Guadalajara, skilled guys are making around 18,000 to 30,000 pesos a month. That's before overtime hits.
Thing is, it jumps fast if you have certifications. Mig and tig experience especially pays extra. I've heard stories of people clearing 40k once they get on with auto plants or oil work.
Where the jobs actually are
Northern states have the most openings. Think border towns and industrial zones. Mexico City has some too but the competition feels stiffer. Real talk, smaller cities like Saltillo or Aguascalientes sometimes have better entry points if you're starting out.

And don't sleep on construction sites either. They hire welders all the time for big projects. Not the cleanest work but it adds up.
Do you need papers or certs?
Most places want at least basic welding certs. AWS stuff helps a lot. Without it you're stuck with lower pay gigs. I've seen guys get turned away even when they're good with a torch because they couldn't show proof.
Language can be a thing too if you're not from here. Spanish helps obviously. But some international shops use English on the floor. It depends.
Look, if you're coming from outside Mexico, visas matter. Work permits aren't automatic. Check that first before you pack up.
What the day to day looks like
Shifts run long. Eight to ten hours common, sometimes more with overtime. Safety gear is usually provided but you better bring your own boots that fit right. Heat in the workshops gets brutal in summer.
Tools get shared on some sites. Others expect you to have your own kit. That can cost extra upfront.
Not great if you hate repetitive work. But the money keeps people coming back.