Ports of call - Mykonos, Rhodes, & Santorini for the day

I would spend more than a day on Santorini, and amybe on Rhodos. It all depends of what you want to do. I personally like to walk around and for sure I would do it on Santorini.

For Mykonos: Wandering the town, shopping, and a few glasses of wine is a good time filler. Delos is worth the trip, if you want to do it on your own, several offices along the waterfront offer transportation to the island. If you are into a party and want good beach, head up to the bus depot and catch the bus to Paradise Beach.
Santorini: Catch the bus to Akrotiri or to Oia, or just sit in Fira town perched at the edge of the caldera.

We just did these islands on a cruise last year and loved them!! Mykonos and Santorini can totally be done on your own-wander the town in Mykonos (see the windmills and have lunch on Little Venice)and take the bus to Oia (for awesome views and photo ops!) on Santorini. We did do the cruise tour on Rhodes to the Temple of Athena in Lindos so that we could get all the information that a tour offers. We fell in love with the Greek Islands, and plan to get back and visit the others that a large cruise ship misses!!

I just came back from a cruise through the Greek Islands and found that I enjoyed doing my own stuff rather than the excursions for two reasons: saving cost and not being surrounded by everyone on the bloody ship. Unless there is something that you're dying to see and time is limited (ie port of call is 6 hours or less), you can usually do things on your own.

Mykonos - Taking the ferry to Delos is a cinch and costs way less than the excursions that were available at the time.

Rhodes - Again, can walk the town, shop, relax on your own. Unless there are specific ruins you want to see.

Santorini - I took an excursion for this one because I was unsure about the travel to Oia, which was a bit father out of the port town.

There are some websites where cruisers have listed exactly how to get to places and do things, you may want to check it out:http://www.europeportreviews.com/#EasternMediterranean

There are links to the bottom left column for each port of interest.

I stayed in Oia on Santorini but took the regular public bus to Fira one day. It was easy and inexpensive. I can imagine it would even be easier doing it the other way around. You do not need a tour guide--just pick up a Lonely Planet or some other reputable guidebook.

We did a cruise with the same stops several years ago. With another couple we rented a car for the day on Santorini. Because of the distances involved and the time constraints posed by the cruise, this is a very good way to see the varied scenery and towns on the island. It is easy driving and enables you to stop where you want for as long as you want. I usually read where the cruise tours are going and put together an itinerary that appeals to us. On the stop at Epidaurus, we hired a driver who took us to various spots, but Santorini is easy to do on your own. Plus we got to the other side of island, Kamari Beach, I think, where I swam. If you like swimming in the sea, take beach shoes because the beaches are all rocky and hard to enter without shoes.

We loved Rhodes and the medival town for resturants and shopping. Although could not get there, the town of Lindos is suppose to very charming and different from the old town. It also has ruins nearby.

We were in the Greek islands a few years ago, and our most memorable day was hiking from Fira to Oai...about 8 1/2 miles. The trail is easy to find.We are going again, by cruise ship, in June and plan to take the bus into Fira from the cruise ship, then change busses for Oai and hike back. The hike is a bit rugged, so take water, but the views are spectacular.