I would put as the first line "OCCUPIED-- DO NOT DISTURB!"     

All of the guests we have had have been very respectful/ clean and I wouldn't even know that they are there if I didn't know they had booked the space (I live on the property and my bedroom window is near the RV so I would have heard any disturbances.)2.)

You can serve a 30-day notice to move if the tenant has violated the lease; late or non-payment of rent, disturbance of neighbors, damages made by tenant or guests to the unit, criminal or drug/ alcohol activity, other violations listed on the lease.I, myself, haven't gone through this process, but I suggest you go through your documents and check with someone from SHRA.

What I find disturbing is a complete lack of reviews online, even for their core business of estate sales for personal property.

If she disturbs them, they should fly away. 

It's generally best to avoid disturbing it, and you certainly don't want to drill into it or cut it if you can help it.

The can decorate the back yard but it can't be an annoyance/disturbance to neighbors.

Depends upon how much of the plumbing is disturbed.

Especially since all REO properties are vacant, so you don't have to worry about disturbing the home-owner.My suggestion is to tell your agent flat-out that you expect to have access to the property as much as need-be.

This is disturbing, and it's one of the reasons I'm happier investing in an area with lower rents than in my home town.