In Bali, the most reliable and convenient transportation is Bluebird taxi. It is well marked and the driver wears a certain type of uniform.
You can come to the airport from the town with a Bluebird taxi. Unfortunately, a syndicate does not allow to take a Bluebird taxi from the airport to town. You need to take the prepaid taxis which is more expensive.
But, there is a way around of this. As, the Bluebird taxi drops passengers at departure hall, all you need to do is to go to the departure hall from arrival hall using the elevator. If you wait there for a while, you will get a Bluebird taxi. Just wave your hand, hop into one and ask the driver to take you to the destination. You will be able to save some money this way.
By the way, Uber or Grab does not work either from the airport, so, the Bluebird taxi is a saviour.