How can I find information on gang related crime in a particular area of Houston?
You should be able to find some good information from the Houston Neighborhood Crime Statistics, listed on this page: http://library.uhd.edu/content.php?pid=94963&sid=1104560. You may also want to look over the library's Criminal Justice Research Guide http://library.uhd.edu/cj.
Also, Houston has a joint effort to stop gangs – you can find the Web site at http://stophoustongangs.org/. One of the participants is the Harris County Sheriff’s Office; their Web site is http://www.hcso.hctx.net/. They have a tool called Crime Reports on their front page that seems to allow you to define a neighborhood and get statistics on crime.