Rather than discussing this in a thread about the diet of expats, I though this would better be discussed in a separate thread (if there's already one about this point, perhaps a mod could merge the two; if this isn't the right forum, perhaps a mod could move it).
What then in your view is the difference between a migrant and immigrant?
Migrants are not subject to immigration control; immigrants are subject to immigration control.
EXPAT: An expatriate (often shortened to expat) is a person temporarily or permanently residing in a country other than that of their citizenship.
I really don't agree with that definition. If it is accurate (and presumably you think it is, as you offer it to us), you would be an expat. But would you really call yourself an expat? I wouldn't. And if is accurate, I am also an expat, but I wouldn't dream of calling myself that anymore. I was one once, but then I realised that I'd prefer this country over my former job, so I became an immigrant instead. Now I'm not subject to immigration control, I'm a migrant. Expats leave their country to perform a specific job and once that job is done they leave the country.
Mirgants are mainly viewed in terms of itinerant Mexican fruit and vegetable pickers.
That will depend on whether you are using the word 'Mexican' to refer to Mexican citizens or Hispanic US citizens. Mexican citizens are subject to immigration control and so would be immigrants, just as you are subject to immigration control here and thus are an immigrant; Hispanic US citizens are not subject to immigration control and so would be migrants, just as I am not subject to immigration control here and thus am a migrant (although a decade and a bit ago I was an immigrant too).