“El Carajo” originally referred to the “crow’s nest on a Spanish galleon”. Now, this was one of the least desirable posts on the ship because sailors would tend to get very sea sick up there due to the ships movements being amplified at the top of the mast (basic physics: mast acts as a lever arm, any movement at its base translates into faster movement over a greater distance at its tip). Nobody wanted to go to EL Carajo.
Consequently, it was frequently used as punishment: sailors would be “sent to El Carajo”, they would be told to “go to the carajo” (“¡Vete al carajo!”), hence the origin of the phrase “Vete al carajo” which it is closest translation to English would be something like “Go to hell”. This in combination with the fact that “carajo” (the place and the word) just took on a very negative connotation in general led to it evolving into a sort of general purpose curse word like our “damn” or “hell”.
Once you arrive to GC you will have a better understanding of the meaning of this cache and its sentence. Being born outside the US believe me this was a common word in my lexicon as I was growing up and back then we would have no idea the reason why we were told to go there so many times lol; I hope that this brief explanation and location would enlighten you on your quest for knowledge 
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