I live in the Centennial Hills section of Las Vegas, Nevada, but my caucus location was at a somewhat nearby High School in the City of North Las Vegas.
According to census data, North Las Vegas is 38% Latino and almost 20% Black. Both higher percentages than in Las Vegas proper. So, in theory, that caucus site, even if divided equally with voters from both Las Vegas and North Las Vegas, should have seen a high number of Latinos/Hispanics and Blacks in attendance. But, that was not the case. While, there were a some Latinos; very few Blacks showed up. It was clearly obvious that the vast majority of caucus goers were white. And, this is a problem.
While Trump can claim getting a higher percentage of Hispanics than both Cruz and Rubio combined; having a high percentage of a low turnout is not a win for anyone. Similarly, Trump winning the highest percentage of Blacks with so few attending the caucus is also nothing to write home about.
Seriously, if the Republican nominee can't attract Blacks or Hispanics in the 2016 November Presidential elections, that candidate won't win. It is simple mathematics when you consider that some states have a high population of Latinos and Blacks. California is 39% Hispanic. Nearly 40% of the population of a state having the highest electoral votes in the country that most likely won't turnout for the Republican nominee; especially if its Trump.
North Las Vegas: https://en.wikipedia.org/wiki/North_Las_Vegas,_Nevada
California QuickFacts: http://quickfacts.census.gov/qfd/states/06000.html