These signs were real. According to Italian newspapers, they were promised (la Repubblica) and then actually installed (la tribuna di Treviso) in 2007 by the mayor of Mogliano Veneto, a town in the province of Treviso in northern Italy, as part of his fight against street prostitution.
It is not an official standard sign in Italy, and it was mostly a stunt to draw attention on the issue of street prostitution, but it seems that the mayor installed it in his official capacity.
The sign is written in Italian and does not seem to have any relation with Spanish profanities, except as a generic illustration for "prostitute". As pointed out by Nate Eldredge in the comments, the wiki talk page indicates that the use of pictures in that article is controversial.
The Wikipedia file page includes the exact coordinates where the picture was taken. Google streetview shows indeed the exact place where it was installed, but it is no longer there.
I could not find specific information on its removal, although this article suggests without much detail that the regional council of Veneto was against prostitution-related street signs.