That is completely wrong. I know several hispanic veterans and any one of them are welcome at my dinner table. They are very loyal to this country.
From personal experience- It's a mixed bag. Some would, some wouldn't. There are hispanic gang members in the military with the expressed purpose of gaining military training and proficiency. Some are sent in by the Zetas, many of whom received their training from the U.S. Military before working for hire in the cartels. The Zetas and other gangs use our military as a out sourced training platform. Their first loyalty is to their gang, not the U.S military or the U.S. Constitution. Also, La Familia is a strong influence for most hispanics. Stronger than than the committment to duty as a soldier in some cases. It's not cut and dry one way or the other.