Small enough to be very friendly but large enough to have most of the facilities for the visitor. There are no banks or ATM machines but there is a great night life which goes on all night every night until the sun comes up. It is still possible to wander off to a lonely beach and see nobody all day. The mountains are for the more energetic. Then there are special places known only to the hostel where you can swim in freshwater pools and shower under waterfalls.
Some people stay for the beach and the nightlife.
The place is also very romantic, you ask these couples, they first met in the hostel.