Short answer. It can be. Article 281 punishes entering the closed premises or fenced estate of another while uninhabited, where the prohibition to enter is manifest and the entrant has not secured the permission of the owner or the caretaker. A posted sign is the usual way that prohibition is made manifest.
What the law says
any person who shall enter the closed premises or the fenced estate of another, while either or both of them are uninhabited, if the prohibition to enter be manifest and the trespasser has not secured the permission of the owner or the caretaker thereof
Revised Penal Code, Article 281 — Other Forms Of Trespass. Read the full provision →
Four things have to be present together
Article 281 reaches any person who shall enter the closed premises or the fenced estate of another, while either or both of them are uninhabited, if the prohibition to enter be manifest and the trespasser has not secured the permission of the owner or the caretaker thereof. Read as a list, that is an entry, into closed or fenced land belonging to someone else, which is uninhabited, with a manifest prohibition and without permission. Remove any one of them and the article does not apply. That is why the answer to the question is conditional rather than a flat yes.
Uninhabited is what marks this provision off
The article is expressly about premises or an estate that nobody is living in. Entering a dwelling against the will of its occupant is a different and more serious matter dealt with elsewhere in the Code, and it is not what this provision addresses. So the empty lot in the question is squarely the situation Article 281 was written for — land held but not lived on, where the owner's exclusion of others has to be signalled rather than inferred from someone being at home.
The fence is not by itself the prohibition
Notice that the article requires a fenced or closed estate and, separately, that the prohibition to enter be manifest. The two are listed as distinct conditions, which suggests an enclosure alone was not intended to do the whole work. A posted sign is the plainest way to make the prohibition manifest, and the question assumes one. Whether a prohibition was manifest in a particular case — whether the sign was visible, legible, and where a person entering would encounter it — is a factual question that photographs taken at the time answer far better than later description.
Permission, and who can give it
The article excludes anyone who secured permission from the owner or the caretaker, and it treats the caretaker's permission as sufficient. That matters on rural or idle land, where the person actually controlling access is often not the registered owner. Someone who entered on the word of a caretaker is in a different position from someone who entered on nobody's word at all. If a dispute has arisen, the useful record is the signage and its placement, the date of entry, and whatever shows who gave or refused permission and in what terms.