In reply to ParaDan:
Yeah, just to echo what has been said above...
Fly to Kos.
10min. taxi ride to the small harbour harbour where the boats leaves. Taxis are always waiting outside the airport. Cost 15eur
The small fast ferry takes about 30min. (7eur), the big ferry 45min. What one you get, depends on when your flight lands. The restruants near the port are fine for diner if you need to wait for the ferry.
Just occasionally it might be too windy for the boats to sail. This happened to us last time. We quickly found rooms at 10eur a head for the night and got a ferry in the morning and were climbing by lunchtime.
Again, there will be taxis waiting when the ferry docks. 20min. to Massouri where you would want to be based for walking to the crags.
I'd not hire a car for the full time. Just as and when required. Transport (car/scooter) is useful if it's very hot and you need to seek the shady crags which are generally a bit further away than the sunny crags around the village.
What you save on car hire, spend in the excellent restruants.
Getting home you'll not want to miss your flight. Keep an eye in the forecast for wind and the potential for the boats not sailing. This isn't usually a problem but it is a thing and does happen. There used to be "pirate" boats that would sail in choppy seas but the authorities seem to have cracked down on these recently so I'd not bank on finding one.
In April you might still find some seepage on the crag so 10% of the routes might still be wet. May-September might be too hot. October generally best but wind at the crags and for the ferries could be a thing.
Post edited at 19:57