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Remember that you can add furigana to your posts by writing ~{KANJI|FURIGANA}~ like:
~{漢字|かんじ}~ which comes out as:
{漢字|かんじ}
この先 could be vaguely translated as "from this point onwards", which usually has a temporal meaning "from now on", but in this case it's meant to be spatial, "don't walk past this sign".
Glad the English translation is still understandable, even if it's pretty funny.
Honestly they should post this somewhere more conspicuous than a hotel in northern Japan if they want humanity to get the message, maybe at the Shibuya scramble or Times Square.