I'm Mexican and I came legally to USA. I have been living here for the past 4 years and I would vote republican without hesitation.
I came to USA escaping the narcos, troglodytes, and others Mexican criminals.
I don't want shitty Mexicans nor any other parasites to come here.
And it's true most Mexicans that come to USA are parasites that want easy money and take it to Mexico. They won't even bother learn English nor adapt to American Culture. 
To me the best way to fix immigration is to negate visas to everyone except students, business owners, and people that want to help the country. If they don't become citizens after being residents for 5 years just kick them out.