You don't say when you are going,but if it's between 15th june and 15th september:

Bus #24 airport to Es Cana every 90 mins from 07.45 to 00.15 cheap and reliable,but lots of stops,not sure of price but probably about 3 euros.

Taxi,not so cheap but reliable,about 35 to 40 euros.

I don't know much about about the little mini coach/island hopper things.