The issue here involves two things: ownership of the trailer and ownership of the land that the trailer is on.  Legally, there is a right to the trailer itself and to visit the trailer.  However, the owner of the trailer park owns the land that it is on.  The owner of the land, and any person who has signed a legal rental agreement for that land, are the only people who have a legal right to be on the land.  Therefore, they have a right to a no trespassing sign.  As the owner of the trailer, you have a right to remove it from the property, but you will have to get an injunction from the court to enter the property for visitation/removal.

The link below is from a California statute, but it gives a good overview.