Eisenhower divulged the date and location of the Sicily invasion to the press corps in May, trusting in their discretion. Since then there have been plenty of stories about Sicily in the news, but I suppose there has been no information that would enable the Germans to zero in on the invasion site or eliminate other possible sites in the region.
I suppose the Germans didn’t really view this as their problem after the loss of their army in Tunisia. Italy was still in the war and should defend its homeland. Besides, Hitler and his generals wanted everything they could put on the Eastern front for their summer offensive against Russia.