Questions of this nature have be beaten to death on here many times in the past.While given the situation described if the adjoining land is not posted I am going on it if it is in a desolate area,if it is an area that is not desolate I am asking the land owner for permission.If denied I will not set foot on it.
Now before the ethics police jump on my back about desolate versus not desolate I would suggest you save your breath.I am completely comfortable with my values,ethics,morals etc.The same person who says they wont set foot on private property spliced an extra TV cable hookup in their existing line or claims things on their taxes that aren't on the up and up or denies their wife basic living necessities so they can purchase thenew this or new that.Only each one of us knows if we are living our lives in accord with doing things right as it relates to the things that are really important!
Me setting foot on land that most people don't have the stamina to get to and is miles from the closest building or residence and is unposted doesn't exactlyput my face on the wall of the post office.In my state I havn't broken a law if the land is unimproved,if it is not posted I can enter it,until requested not to by the land owner.
We have significant amounts of mountain land that has been and continues to be purchased up by the Department of environmental protection,then they post it heavily.In many instances it is extremely desolate and the signs say no entry for any reason.Try that on for size,your tax dollars have helped to purchase rugged mountain land and you can't set foot on it for any reason.Your tax dollars bought it,it comes off the tax rolls and no one can use it.Welcome to New York State!