That's according to this piece from Reason magazine, which quotes several criminologists who say that El Paso, San Diego and other cities with large illegal-immigrant populations tend to be much safer than other communities. (This is especially remarkable in the case of El Paso, which is directly across the border from Juarez, aka The Mouth Of Hell.)
It's an interesting piece, though they don't talk much about drug-related crime. When they say low crime, it seems like they're mostly talking about violent cases.
Hat Tip: Saw this via Andrew Sullivan!