Hi. I visit Datca regularly and have done so for the past 16 years, I think you will have a wonderful time.
Asina hotel looks very nice and is on a cliff a few km's out of town. It is a bit of a walk into town for the evenings. The harbour is great for restaurants and I tend to frequent Beyaz Amca, Papatya, Maradonnas, The Captains Table, Culinarium but there are several more good ones. For the stunning views and nice food the Panorama restaurant is hard to beat and I believe the manager will send a car for you as the walk there is steep. There are some nice bars also with Yasis, Mir mir and Bolero being my personal favourites on the harbour side. There are plenty more though and you will get slightly cheaper prices if you venture away from the harbour and try perhaps the restaurants along the beach by the school. There are many back street places worth a try for much cheaper but very good food. Although you don't need a car if you only want to hang around your hotel or town you would find it beneficial if you want to explore the peninsula. There are some truly wonderful spots with quiet beaches and fantastic views. Knidos at the end of the peninsula is a 'must see'. Expect to pay about 50 lira a day for car hire in Datca, there are a few car hire shops. A nice pebbly beach near your hotel is Kargi Koyu. The walk is beautiful but you may wish to flag down a bus which passes near your hotel hourly. There is a lovely restaurant with gardens and beach beds. The white ducks live there and you sometimes find goats on the beach. If you want a sandy beach you need to drive for about 20 mins to Karaincir or just before that Perili Kosk beach where there is gravelly sand and a small water park. You can also catch buses there from the town. Other things to do would be one of the daily boat trips, reserve your place the night before with one of the captains in the harbour. We usually go on the Gozde but there are others. You can visit Knidos by boat or just get a trip that stops off in some of the many bays for swimming. Symi is a day trip to a Greek island and well worth the trip. Datca hosts a good market on Saturdays and you must visit that. Haggling is required there! A very interesting lady to visit is Stella near the harbour she has an amazing carpet shop and won't hard sell. She is an absolute expert on antiques of all kinds and so interesting to talk to. Her English is very good and she is very exotic with unusual clothes and hair styles. She is the only woman I know who can put clothes pegs in her hair and look glamorous!! You can pick up small items for reasonable prices. I love the old embroidery on silk. Another nice man is Serin with the Ottoman shop, I buy ceramics from him. There are a few very good jewellers and another shop selling scarves etc. I have just stocked up on silk scarves and pashminas from there for Christmas!!If you need any more info or links to photographs please pm me.

Thanks for a really helpful reply JMK. To be honest we would rather be a bit closer to the harbour/ restaurants etc. Can you recommend a hotel that's a bit nearer to the town please?

I think the Asina is very nicely furnished etc although I haven't been in it. It also has beautiful views. Last year my house was overflowing and we put extra people in the Mare hotel which was very nice by a beach with a pool and garden and 10 mins along the prom into town. It has a web site and some of the staff spoke English. Club Datca looks quite nice and is 15 mins walk along the same prom. Fora hotel is in the town by the beach but no pool. Turkish House is a really nice small hotel but has no pool. If you are looking for transfers we use Marmaris transfers and have always been happy with the service. Sometimes we get a cheap shuttle transfer to Marmaris and then pick up a hire car there. You might also consider renting a villa. There are several web sites with Datca rentals. Just be sure to check where they are as most are a fair way from the harbour. Do ask me if you need more info.

I've hunted high and low, but cannot find the Mare Hotel - have you their web address please?

http://www.hotelmare.com.tr/web_16390_2/index.aspx
hope this works.
It's worth phoning or emailing them to try to negotiate a discount especially if you are travelling in the lower season. Datca is a quiet place and hotels only really fill up during the Turkish school holidays.
Another one to look at is the Uslu hotel but we found they didn't answer our emails. We have stayed there and it has a very good position and nice pool. The rooms could do with some updating although they were clean enough and the staff very helpful.

Thanks again, I'll contact them.

Hi JMK, just to say a big thank you for all your advice, re transfer, restaurants etc. We got back yesterday and had a great time at Villa Asina hotel. We used Marmaris Transfers and everything went smoothly. We also tried a couple of restaurants that you recommended - excellent. Will now start looking for next year's desination! Thanks again.

I'm so glad you enjoyed it but I felt sure you would. This is an area that more people should venture to especially in the lower part of the season ie June and September. No English bars, no mass tourism, very few european tourists, fairly undeveloped, mind blowing scenery and blue flag beaches.