The book that Cameron said he went back to get from his room is "Gone Bamboo" by Anthony Bourdain.
When Jack and Portia are sitting by the water talking about goals you can see a tattoo of crossed hammers on Jack's forearm. This is the logo of West Ham United Football Club. Later, when they're walking through the streets he starts singing 'I'm Forever Blowing Bubbles,' the anthem of West Ham.
Although the hotel used for filming is in Taormina, the beach scenes were filmed at Cefalù, over 200km away. Parts of this episode cut between scenes of Jack and Portia visiting the real Cefalù, and Cam, Daphne, Ethan and Harper on the beach, supposedly at Taormina. In fact all of these scenes were filmed a few hundred metres apart at Cefalù.
Opera in Palermo would have taken place at Teatro Massimo.