Hi! Looking at the complex you've chosen it is actually in either the Mangum Manor or Mangum Plaza neighborhood, not Oak Forest. I would highly recommend you contact the Houston Police for their most current crime statistics for the area and that complex specifically. It may help to add this is part of police beat "3B10". That will let them know what exact patrol this is part of to further narrow down the crime rates for you. I have included a link to the website with statistics for that area below.
One other piece of advice would be to speak to your potential neighbors. They will be the one of the best possible sources of information to give you an insider's view of living there.
Good luck in your home search!
crime info : http://www.houstontx.gov/police/cs/beatpages/cs3b10.htm
map : http://www.houstontx.gov/police/cs/beatmaps/3b10.gif
registered sex offenders in 77092 : http://www.city-data.com/soz/soz-77092.html