John Kelly had a column in the Post about the origins of DC cabdrivers. (Not sure the link to the list will work.) Here's an excerpt. Driving Around the World in D.C.: "Topping the list is Ethiopia. Of the 4,990 drivers that the commission has information on, 1,383 were born in that East African country. Next up was the United States, with 1,047."
What's notable, given that Latinos dominate in our immigrant population, is the absence of countries below the border. Why is that, I wonder?
Kelly's column suggests one answer is education/language. My impression is that most Hispanics who emigrate are lower middle class (they've got enough money to pay the coyotes but not much more). They might be uncomfortable navigating the bureaucratic ropes needed to learn to drive and get a cabbie's license, and dealing with customers. At least one driver he rode with had a college degree and suggested it was a good stopgap job.
Another answer might be the first-mover phenomena: an initial pioneer comes to the U.S. and finds a job, he tells his relatives and neighbors back home and they follow. That's one reason for Irish cops in NYC, Koreans in groceries and dry cleaning, and Patels in motel ownership.