transportation on Sicily

Here are some things I found by Googling that I hope help. According to the Lonely Planet website for Agrigento there's a bus from the town to the Valley of the Temples: http://www.lonelyplanet.com/italy/sicily/agrigento/transport/getting-around. Then you have to go back to the town of Agrigento to get a bus for the other locations: http://www.lonelyplanet.com/italy/sicily/agrigento/transport/getting-there-away. I Googled the first listed bus company, Autoservizi Cuffaro and found this by guess and by golly clicking on the links, all in Italian: http://www.cuffaro.info/orari-e-partenze-cuffaro-autoservizi/palermo-agrigento.html. I also checked Lumia for the Agrigento to Trapani (Erice) route and found this Lonely Planet info: http://www.lonelyplanet.com/italy/sicily/trapani/transport/getting-there-around. It includes the bus to take from Trapani to Palermo. Finally, I found this Lonely Planet exchange about the Agrigento to Siracusa part of your question: http://www.lonelyplanet.com/thorntree/thread.jspa?threadID=2300818. (The linking didn't work for it.) Then I pooped out. Looking at a map of Sicily you are going to widely different locations all over the island. From what I could tell you can get to all of them, but you will need to use a variety of public transportation services and plan well.

Becky, this might be one of those instances where you should trust that you'll be able to figure it out once you get there. When you get to Agrigento, find a travel agent and ask them how to get to Siracusa. Same thing with Palermo. I'm a planner too, but it actually adds a bit of adventure to a trip to go without every detail planned. And it has always worked out for me.