Mexican :

At the 2010 census, there were 319,263 Mexican Americans living in New York City. In 2009, in the new-york’s hispanic population, 13.5% was Mexican. Mexicans are the fastest growing group of Hispanic population.

Census of Ethnic concentration in the Bronx in 2000 :

http://upload.wikimedia.org/wikipedia/commons/3/3e/Bronxrace.PNG

We can see in the west and in the south of the Bronx there are a big concentration of hispanics. The hispanics live in the Bronx because it’s a poor borough.