Statistically true is a somewhat nebulous thing.
There is a large segment among the Faux News crowd who would tell you that an illegal alien is in the country illegally, so is by definition a criminal, making the crime rate 100%. That is the crowd Trump is trying to appeal to, so the real issues of likelihood to commit other crimes are somewhat irrelevant.
As far as genuinely answering your question, to determine the proportion between those having additional crimes and those that don't would require determining the actual total number we are dealing with. This is complicated since, obviously, getting a complete census of illegal aliens is not a simple task. So, if we depart the realm of the Faux News headline that they are all criminals we enter a world of uncertainty where Trump can make any claim, no matter how outlandish, and not be concerned that there will be actual facts to get in his way.