Well, since the thread is getting lots of replies anyways, I'll throw one in the hat...
In a December 17th, 2014 post, where you posted the same basic question, you included pictures of the signs on the door. They read "ATTENTION: This
property is either in the custody of or owned by the Department of Housing and Urban Development (HUD). Trespassers will be prosecuted to the full extent of the law. All representatives of approved Sales and Asset Management firms, including those authorized to perform repairs and any others, must clearly identify themselves on the sign in sheet located inside and record and explain the purpose of each of their visits to these premises."
You posed the question, and interpretted that since the sign was on the home, and not posted in the lawn, that it applied only to the structure.
It seems that an easy clarification would be to focus on words in the memo, and cross reference that with HUD's definition of the same.
For example, the word "property" in the memo, which you've defined as the structure on which the notice is posted, according to HUD is defined as:
Property (Fixture and Non-Fixture): in a real estate contract, the property is the land within the legally described boundaries and all permanent structures and fixtures. Ownership of the property confers the legal right to use the property as allowed within the law and within the restrictions of zoning or easements. Fixture property refers to those items permanently attached to the structure, such as carpeting or a ceiling fan, which transfers with the property.
So, property, by this definition, includes land.
(source:
HUD - Glossary)