Make sure to check with the local YMCA.. they usually offer free boxing and lately some have offered free kenpo or other form of karate.
If you can't find anything out there, let me know and I will ask my friend who teaches Shodokan to children.. he is a 3rd degree blackbelt so I can guarentee you that he will know something.
(he was also my sparring partner in Dallas before I moved, so if he wont give me the information I will beat the information out of him!)