I agree about being able to grasp the gist of the message with some basic Japanese, but IDK about being able to actually read the message.

　お願い

　この先は危険ですので、これ以上前へ行かないようお願い致します。

There are some parts of the message that I don't think is included in basic Japanese lessons:

• 危険 → dangerous
• 以上 → exceeding, beyond
• 行かないよう → probably related to the V+ようだ construction, which with the following bit, might be a polite way of making a request.
• お願い致します → probably some polite way of saying ‘please’

If I were to translate the message with my meager self-taught Japanese, I'd probably render it as something like

Request

Because of the danger ahead, not going beyond here is humbly requested.

Though I don't think that fully captures the nuance of the message itself.