Can I put a lien on a person's personal belongings if they have been repeatedly asked to move them off my porch and they refuse to get them out

A)  No.  Absent a contract or a statute which allows it, you can't assert a lien against someone's property.  At any rate, a lien is a security interest in an asset used to secure a debt.  You haven't claimed that this party owes  you any debt.   B)  Why would you want to?  How is a lien going to help you get rid of the stuff?   You dont refer to any contract or any basis why you should be obligated to continue to store these things.  Unless Florida law is different, I think you can just advise the person that if he doesn't make arrangements for his stuff in a reasonable period of time (30 days should be plenty) you're going to get rid of it.