Didn't say a lot were from Argentina, said some were. If 2/3 of the population is Hispanic(look it up) and I assumed they were from various countries in Latin American, still a good assumption I think. Since most of the population is Hispanic its safe assume that most of the crime is also perpetrated by the Hispanic population, is it proportional to the total population, 80%, 60%, I don't know but I'm sure its over 50% which still equals most.
Since crime is related to inequality and social networks, you should look more into the American system and its particular aspects in Miami and less into the ethnic background of each individual. The same "latin" guy in Norway maybe could be working or receiving his unemployment check, and in Miami he could be stealing or something else.