The transport from the airport to Hydra can be included in the registration price as indicated on the registration form. The transport from Hydra to Athens must be arranged when you reach the island of Hydra, as return boat tickets are only available on the Greek islands. Boats are numerous and leave on a frequent basis. To return to the airport from the port of Piraeus, you can either take a taxi, or the metro to the airport bus.

As for international transport to and from Greece, you can arrange this on your own or if you want Sun and Sea Travel Agents to arrange it for you, fill in the appropriate page on the registration form. It has been my experience that often tickets bought in Greece are cheaper than those bought elsewhere, but you might want to do some price comparison before you commit!

If you are planning to return to the US on the Monday after the conference, I would advise you to arrange to spend Sunday night in Athens from which it will take less time to reach the airport for an early morning flight. Spending Sunday night on Hydra would mean taking a 07:00 boat back to Piraeus.