This article has a map showing the greatest concentration of M-13 gang members are in California, New York, Virginia and North Carolina (last one is surprising) -lesser presences in other states shown. 

Simple equation, open borders with unimpeded access by invaders = more M-13 members slipping in and more gang activity.  In the Atlanta area we've already seen a rise in violent crime such as take over bank robberies, car jackings and brutal home invasions..... and we have a lesser presence of them but there's been plenty of graffiti left by gangs.

"Vicious MS-13 gang seen as growing threat
Authorities target group in Texas and across U.S.
<excerpt>
07:49 AM CST on Sunday, October 29, 2006
By DAVID McLEMORE / The Dallas Morning News

"PHARR, Texas – Shortly after midnight in late September, a Texas National Guard soldier with night-vision equipment spied four figures slipping through the brush and alerted Border Patrol agents.
The men were arrested, and one in particular stood out for the extensive tattoos across his face, body and arms.
A fingerprint check showed Santos Chileno-Gomez, a 23-year-old Salvadoran, had been deported for an assault on a Long Island, N.Y., police officer. His lengthy criminal record – and the tattoos – labeled him as a member of Mara Salvatrucha 13, a vicious international street gang that federal authorities call one of the most violent in the U.S.
Mr. Chileno-Gomez is among 76 MS-13 members apprehended by the Border Patrol in the Rio Grande Valley during the just-ended fiscal year. That total was up from 62 the previous year, showing the gang's resilience to federal efforts aimed at rooting it out and its determination to travel almost at will through Texas to cliques operating throughout the U.S.
And, some police agencies believe, there is evidence that MS-13 has taken sides in the bloody war among drug cartels that's playing out in Nuevo Laredo.


http://www.dallasnews.com/sharedcontent/dws/dn/latestnews/stories/102906dntexMS13.2e3e193.html