If your goal is to improve treatment of prisoners at the jail then contact the ACLU as Cica suggested. They are the group that is typically interested in human rights cases and causes. By doing so if there really is a huge problem with how the inmates are being treated they will get it addressed. YOU won't profit from it but the inmates will be better off.
If you are looking for a huge windfall from your stay there you can pretty much forget about it. Feel free to call around to a few attorneys but as I said in my other post I don't see any attorney taking the case on contingency (% as you put it) and others have told you this as well. The odds on winning aren't good. You don't have any damages. In order to win a case like this you have to have damages. Even if you are willing to pay an attorney you are talking hundreds of thousands of dollars to try a case like this. Plus you are also talking about suing the state. They can always claim sovreign immunity and the whole thing is dead in the water.
Contact the ACLU. If it has merit they will address the jail conditions.