You have been notified by the sign as far as our law is concerned. I don't know if the courts wil end up treating it differently than face to face notification.
As I recall Act 35, even the instant existence of the sign is not required. Proof of its previous existence is sufficient.
I'll find the cite in a moment ....
ETA: Section 81
SECTION 81. 943.13 (2) of the statutes is renumbered
943.13 (2) (am), and 943.13 (2) (am) (intro.) and 1., as
renumbered, are amended to read:
943.13 (2) (am) (intro.) A person has received notice
from the owner or occupant within the meaning of sub.
(1m) (b), (e) or (f) if he or she has been notified personally,
either orally or in writing, or if the land is posted.
Land is considered to be posted under this subsection
paragraph under either of the following procedures:
1. If a sign at least 11 inches square is placed in at least
2 conspicuous places for every 40 acres to be protected.
The sign must provide an appropriate notice and the
name of the person giving the notice followed by the
word “owner” if the person giving the notice is the holder
of legal title to the land and by the word “occupant” if the
person giving the notice is not the holder of legal title but
is a lawful occupant of the land.
Proof that appropriate
signs as provided in this subdivision were
erected or in existence upon the premises to be protected
prior to the event complained of shall be prima facie
proof that the premises to be protected were posted as
provided in this subdivision.