The thing that keeps Datça quiet is the thing you have to plan around: it is not quick to reach. There is no airport on the peninsula, and the last stretch of road is slow by design. None of it is difficult, but a little forethought turns the journey from a chore into the gentle decompression it should be.
Most people fly into Dalaman, the nearest airport, well served in summer from across Europe. From there it is roughly a two-and-a-half to three-hour transfer by car or coach along the coast and out onto the peninsula. Bodrum airport is an alternative and adds a short car ferry across the gulf, which some travellers rather enjoy as a scenic start to the holiday; either works, so book flights by price and time and sort the transfer to match.
The transfer itself is worth getting right. A pre-booked private car is the easy, door-to-door option, especially with a group, luggage or a villa deep in the villages; shared shuttles are cheaper but slower and stop often. If you are renting a car for the week anyway — and on the peninsula you probably should — picking it up at the airport and driving yourself is the most flexible choice.
That last hour is part of the trip. The road out to Datça climbs and winds through pine and olive with the sea opening up on both sides, and at one point the two coasts come so close you can see water left and right at once. Take it slowly, stop at a viewpoint, and let the pace of the peninsula start working on you before you have even arrived.
Once you are there, a car earns its keep. Datça town is walkable, but the coves, the villages and Knidos are spread along the peninsula and taxis are few. For a relaxed week of drifting from beach to lunch to viewpoint, your own wheels are less a convenience than the whole way the place is meant to be seen.