Upvote:3
Yes, it is. If you go to this online-bus map, you will see that there are tons of stations all over the island. Zoom out of the google maps and check the tickbox "bus stops" in the orange field above it. I am sure you will find one near where you want to go. One of the longest routes from downtown Naha will take you only 3.5 hours, provided you take the highway bus as suggested by the route finder.
Otherwise, there are also ferries, but I would assume that they are much slower than the bus unless you want to go to another island.
There is also a small train (1 line only) from the Naha Airport to downtown Naha.
Taxis are always a (not so cheap) option too, of course.