I'm just a "country boy" so I wouldn't visit Miami much less live there. From my understanding you have to be fluent in Spanish or some other type language that I will never learn.
Like any other large city if you have a lot of money then you'll live in a nice, crime free neighborhood. However by just doing a little search online I saw a commit:
Reese, , Miami, FL
"There is crime everywhere in Miami. My suggestion to you would be to stay far, far away from this awful place."
I wish you luck however.