I think this about the worst city for riding cause their aren't many places anyone oppose? I've seen more spots but I woukd rather not get shot, and I'm not always looking to drive a couple hours just to ride for a little while
I think general sams is mostly mud. Down south off-road in crosby is supposed to have some good trails. Also, there is the sam houston national forest in huntsville. Since its a state park they have some restrictions but ive heard its not bad.
I just got my quad so i havent had a chance to make it out anywhere yet but i know people that go ride in the forest all the time and like it.
Down South offroad is on the river too, good place to cool off after riding.