Ahh, sucks that the tourist beat us to it.....

The answer to the puzzle:

SFHLHL STJZ JFJP UE ZFSFDOU

becomes

Curara Cito Tute Et Jucunde

It is an ancient greek medical formula.

To arrive at the answer you must shift the non bolded and bolded letters by a different amount.

Replace the non-bolded letters as follows;

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
K L M N O P Q R S T U V W X Y Z A B C D E F G H I J

Replace the bolded letters as follows;

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
P Q R S T U V W X Y Z A B C D E F G H I J K L M N O

So that gives

S F H L H L _ S T J Z _ J F J P _ U E _ Z F S F D O U
C U R A R A _ C I T O _ T U T E _ E T _ J U C U N D E