When we went to DV, we walked down every morning to clear our heads (lol). It takes about 20-25mins, but it's all downhill so it's not difficult.
There are also a couple of nice cafes on the walk down that you can stop off at if you fancy a coffee or breakfast. (Beccy's Cafe).
What we did was drive down in the evening and leave the car in the free car park in the marina, then get a cab back at the end of the evening, it only costs c8 euros.