When I did my CNA training I couldn't find any that were for free, the cheapest I found was about $500. This is where I found the school, it is a list of all accredited Nurse aide schools from the texas registry in this area:
http://www.dads.state.tx.us/provider...egionselect=03
Also I hear El Centro college in downtown has a LPN program, you might want to look into it.