I just got back from olu deniz after an amazing 10 days! So here are some tips and advice for you :-)
Trips and tours.
I highly recommend to book all your trips from a company called guide tours. There is a very nice american lady called Tara, who works for them. She is trustworthy and honest and I could not fault any of their tours. We did 2 tours, a boat trip and a trip to the Lycian ruins and the canyon. Amazing trips. I highly advise you speak to her. Her office is on the main road into olu Deniz. You can't really miss it!
I recommend doing the following trips: boat trip 6 island, canyon trip, a bus ride to kabak which is amazing, kayakoy and definitely the Tuesday market in fethiye. There are plenty of other trips too, but I didn't have the chance to visit them!
I did it with sky sports for 200 lira. Re action are the best as I was told since they have an extra qualification. You can get it as cheap as 130 lira, but then you don't know how trustworthy they are. Pay extra and stick with sky sports or reaction. Oh and don't bother going to olu deniz if you don't do paragliding haha
Turkish sellers etc
Whilst people there are lovely at the end of the day all they want is your money. As a general rule, don't trust the native Turkish population. They will try and rip you off! See if you can find some westerners who generally more honest.
Don't buy them. They will break quickly!!! Just a tip!
34 degrees and getting hotter every day. Ensure you have lots of sun cream and be careful. It's so easy to get burnt without knowing it even if you are careful!!
Beers generally between 4-6 lira for a pint of efes. Blue lagoon entry is 5 lira. Sunbeds and umbrella are 18 lira. Food. Kebabs from the take away is always a good cheap choice at 8 lira and it's all delicious! Meals in restaurants will set you back about 60 lira for 2 drinks a starter and 2 mains. Some restaurants and cheaper and some are more expensive. Safe costed me 2 pounds a day and aircon was 4 pounds a day. May differ with hotels. dolmus prices range between 3-6 lira depending in where you go. Large bottle of water 1.50 lira, beer 3.50 from shops.
I was there when the 6.1 earthquake struck. Scary experience but nothing was damaged in olu Deniz. Most damage was in fethiye. Don't worry about it. It's perfectly safe!
Can't think of anything else, but if you have any questions please ask me and I'll be happy to help as the other have helped me here.
Apart from that. Enjoy your holiday. You will love it!!!!