Awareness is not really necessary. Even in the absence of a fence and "No Trespassing" sign, they can still get you for criminal trespass. If, for instance, you go onto old lady Johnson's lawn and help yourself to all of the spinach in her garden or the roses in her rosebush. (Well, assuming she wants to press charges that is.) She doesn't have to have a fence or "No Trespassing" sign.
That's why they'd charge you with misdemeanor theft and criminal trespass. (Unless for some reason old lady Johnson's flowers and veggies were extraordinarily valuable on the open market.) If old lady Johnson is the prosecutor's grandma, you'll also likely see a disorderly conduct charge. And you'd better hope you don't live in a jurisdiction with robust menacing statutes.
Point is, any prosecutor can start stacking these charges and land you in a world of hurt for whatever reasons they please.
I remember vividly a night in college when I got a ticket for underage drinking at a house party. I was wishing I had gone with my friends to a bar downtown. Until they got back later that night and I found out that a bunch of them got cited for underage drinking, disorderly conduct, and also got forgery charges. (Because of the fake id's they used to enter the bar.) In essence, they had done the exact same thing I did, only difference being the cops that busted the house party didn't search everyone and find fake id's on us. All those other charges were totally unnecessary, but they got stacked on anyway because the prosecutor and/or cops wanted to be hard asses.
