I was looking at this schedule from Wiki. Looks like there were 2 shows on MS-13.
Episode Title Air Date Details
Special Aryan Brotherhood Thursday, June 24, 2007 Aryan Brotherhood
1.1 American Gangster Thursday, November 1, 2007 Frank Lucas and Leroy "Nicky" Barnes
1.2 Kings of New York Thursday, November 8, 2007 Latin Kings
1.3 You Rat,You Die Thursday, November 15, 2007 MS-13
1.4 Code Of Conduct Thursday, November 29, 2007 Mexican Mafia
1.5 Behind Enemy Lines Thursday, December 6, 2007 Hells Angels
1.6 Stone to the Bone Thursday, December 20, 2007 Black P. Stones
1.7 Hate Nation Thursday, December 27, 2007 White Power Skinheads
1.8 Gangster City Thursday, January 3, 2008 Gangster Disciples
1.9 Blood in, Blood out Thursday, January 10, 2008 Nuestra Familia
1.10 Basic Training Thursday, January 17, 2008 Gangs in the military
1.11 Blood Oath Thursday, January 24, 2008 United Blood Nation
1.12 Root of All Evil Thursday, January 31, 2008 MS-13
2.1 Maniacal Thursday, March 13, 2008 Maniac Latin Disciples
Looks like they already started season 2 though.
I just watched the one on the MLD. Apparently they operated mostly in a park just a couple of miles from downtown. I'm not sure which gangs concern me the most. The organized military type, or the unorganized all-for-yourself type.
I saw that my dvr just recorded a San Fransisco episode.