Central American gang violence is pervasive in the daily lives of millions and is well documented. The links below have useful information, but be sure to check the resources under "Where to Start" tab.
Women on the Run is a 2015 UNHCR report specifically discussing the impact of gang violence on women and how it relates to international refugee law.
Presentation by USMILGP-ES (2007). Warning - some slides have graphic images. See slide 10 for gang presence. Also has information on gang written languages, hand signals, graffiti, tattoos.
Gang Tattoo, photo from U.S. Immigration and Customs Enforcement