Kosman - you'll have a lovely time. I found Oia so relaxing and beautiful. I can't comment on most of your questions, but as it relates to the last re: reservations, I don't think you'll have any problems. Early June is still not high season, so I think you'll be able to make reservations when you get there. We were there in late September & had no problems. (We enjoyed both Ambrosia & 1800.)

As for the cruise ship traffic and best time to do the sailing excursion, I didn't notice much difference in cruise ship traffic from day to day. In Oia, folks are bussed up there to see the sunset, so there are throngs of people there early evening. (We found that by just sitting on our patio looking out at the water and enjoying that time with a glass of wine, while folks cleared out, was perfect. Then when you head out for dinner, things have settled down.) So from the Oia standpoint, doing the sailing during the day won't make much difference as to the day. We did the trip, going over to hike the island with the semi-dormant volcano (very cool!) and then stopping at another point to swim and then get lunch, was fun with a large group of people. I don't know that a semi-private group would have made it better.

As for the hike to Fira, we didn't do that, but the island isn't large and the direction will be obvious. There may well be maps but I bet you won't need it. (We did hike down from Oia to the water, and had a nice lunch at a little water-side spot. Great calamari.) I would recommend against riding the donkeys down. From what I can tell it's a great way to get your legs skinned against the rocks. You'll see what I mean.

I wanted to do the winery as well, and we didn't want a car, so we decided to wait til our next trip, which we decided there would have to be, since it's so lovely! (We'll combine with Istanbul next time.) The ATVs are everywhere, but I imagine it is longer than you'd want to drive, though others may have a different preference. The bus system is easy (we took a bus to Fira and back, so that may be an option.) Enjoy!

Is there any reason for not renting a car? It makes getting around so much easier, although the bus service is good it can be very crowded. ATVs were a real pain to drive behind, not to mention dangerous on those curves. You can get to Kamari and Perivolos beaches easily without worrying about the bus service, plus you can try some restaurants outside of Kamari and it's tourist strip.
The tavernas we enjoyed the most in Oia was at Ammoudi, the ones in Oia were more expensive, at Ammoudi they were more authentic and laid back (& the horta were to die for!!) I didn't find Oia quiet, it was buzzing all night with people walking up and down. Its a long walk from Oia to Ammoudi, esp on the way back! I did not see donkeys but saw mules, donkeys would not be able to manage carrying people up and down and only saw them in the day.

I didn't rent a car on Santorini and had a little trouble with buses and taxis. Maybe if you are sure you don't want a car, you could ask your hotel for advice on some of your transportation-related questions? I am still kicking myself for not checking with our hotel prior to arrival because they would have helped us get from the ferry port to where we were staying on Kamari.

We rented a car for a day or so, easy and inexpensive arranged by our hotel. We saw ATVs and they looked very dangerous driving on those twisting roads.
We used the bus to go to Fira and back during our carless days. Walked to Amoudi Harbor and back which was my favorite place.

Odin - Sorry, mules I'm sure you're right. Needless to say - don't ride them!

I absolutely loved Oia also - it's breathtaking! I did the catamaran sailing tour with Captain Ted and it was so much fun. Ted and his team are very organized..we had lunch on the boat and it was an all-around great experience. I would definitely recommend. One good after-dinner taverna is Red Bicycle in Oia..we really enjoyed it. You will find several tavernas as you're walking down the pretty streets of Oia. Also, definitely plan for dinner one night on the water at the bottom of the cliff. It's about a 100 steps or so to get down there but very much worth it!

We went last year and rented a car from this company: http://www.santorini-Car-Rental.com
It was cheap and good. I highly recommend renting a car so you can explore the island. The walk from Fira would be VERY long. We visited several wineries, all on one day, but they would not be easy to get to by bus.
We had a wonderful trip and Santorini is beautiful. I'm sure you will love it.

Thank you, so much, for the thoughtful responses!
Dunia123: thank you for clearing up my concern with cruise ships! Now I see that it would make little difference. Did you like Ambrosia or 1800 better?

After reading the posts, I think the ATVs sound a bit too dangerous. I guess my hesitation with the car is because it seems like a lot of work lol. I am also worried about drinking and driving (coming too and from the winery, especially). It seems like though you would need a car to get to the wineries.

Sand22 - Great to hear that you enjoyed the tour with Captain Ted! & thank you for the red bicycle suggestion - we will def put it on the list

Kosman - I would say I probably enjoyed 1800 a little better - we sat up stairs in the open air, and it just lovely with candles. Such a beautiful island!

There was another restaurant that we liked quite a bit too, had to google details to remember the name: Kyprida http://www.kyprida.gr/. The owner is from Cyprus. One of the desserts was fantastic (Kounefe I think) - I still have the notes I wrote on a little piece of paper sitting on my desk, and this was a little over 3 years ago!

Don't miss the amazing seafood restaurants in Amoudi Bay, which is all the way down the big staircase at the end of town in Oia. We had some of our best meals there, and it's a lovely spot for early evening drinks.

Dunia123: thank you thank you for taking the extra effort to find the name; we would like to try a different place each night so I will add kyprida to this list. I'll follow up with a trip report when we return!

Weadles: sounds lovely! Is there a restaurant in particular that is a favorite?

Best taverna in Ammoudi, and most popular among locals is Katina.
This is where you get real greek food, i would also like to recommend another restaurant, Anemomilos, at the same named Hotel. It is very simple, with low prices, but they serve delicious meals !!! ( no comparison to 1800 of course....)

Best restaurant in Santorini IMO at the moment is Selene, they offer amazing new greek cuisine, based on local high quality products for which Santorini and the Cyclades are famous in Greece.
Selene is located in the village of Pyrgos.

We ate in Katina 2/3 times as it was the place we enjoyed most, above all the more expensive restaurants. We also ate in Kyprida, and the owner is indeed a "kyprida", it made a change to have Cypriot food, the afelia was very good (pork is always excellent in Cypriot cuisine) and so was the mastic ice cream, which I always look for when in Greece/Cyprus (that and old fashioned rose water ice cream which I can't find easily anymore). The most fabulous pastries we had were from a "fourno" (baker) on the main road into Oia.

I've been dreaming of going to Santorini and just had to bookmark this...it's going to be our empty nest trip (if the kids ever move out that is!)

Kosman, I will be doing that Fira to Oia walk on May 12th, weather pending when our cruise visits for the day. We also have intentions of once we get to Oia to go down to the water edge and have a nice lunch. I will report back, if you like, about those aspects when we return after May 19th.

Kwren...alas, they always come back. LOL