Frustrated with young man

I am very frustrated with a young man, 18, tempararily living in my home.  He is my nefew and was diagnosed at the state mental hospital last Dec, (Dec 2008) with paranoid schizophrenia.  He moved in with his mother after he was released, and because he refused to take his medication, and go to treatment, she asked him to leave.  He has been homeless and in jail a number of times, finally my husband and I took him in with the understanding we are his last hope in getting on the right track. 

He did ok, for a few weeks, did what he was asked, worked on getting treatment, but since the state is slow about approving treatment for him, he has no patience.  He now gets some money from SSI, and has medicare, he gets food stamps, so he buys some of his own food.  We are working with a community support group to get him into a group home, another thing that takes time.  He has a social worker see him 4 to 5 times a week for up to 20 hours a week.

But what has happened recently is he has been acting out.  First he atteneded church regularly, but today he said he is no longer going and just wants to sleep all day.  He went out with friends, and acts up...saying foolish things, going on My Space and Facebook to connect with girls so he can solisit sex from them, and talking about drinking and sex all the time.  People don't like being around him because of his strange behavior.  And his acts of sexual nature have landed him in trouble with the law again.

We have told him a number of times he has to work on getting himself in a better place. But he has to understand alot of people are trying to help him if only he will help himself.  If he messes up another interview to get into a group home, I think we will have to put him out.  My husband and I both work full time, and we are begining to not trust him being in our home.

His sister lives here also, and she really does not want him around either because he is always walking in on her dressing or showering.  He even broke her door lock trying to get in.

I know he takes his meds, but I do not think they are the right dose, since his behavior has deteriorated badly.

If only we could get him to see he has to help himself, and stop with the destructive sexual behavior.  He tried to get a 12 year old girl to have cyber sex with him.  His computer was taken away, since we can illafford to have him bring more legal actions against him and ourselves.

Perhaps other care givers can help me get through this, tell me some of the things you do to help your loved one.  He can be a very wonderful, happy man, right now he is just out of control, and headed for homelessness again.