You get along with English in many cases in Naha
The island of Okinawa is situated in the very south of Japan and also in quite a distance from the mainland (about 500km from Japan but only 125 km from Taiwan) and from 1945 till 1972 Okinawa was totally under US-control. Untill now it is still used as an american military base, so that is one of the reasons why the local people are a bit more used to talk or understand some english and you will also find a lot more english inscriptions than on the mainland of Japan.
On the total it was quite easy for me to get along and find my way to the castle and finally a taxidriver to take us back to the ship.
In any case we had been prepared also by our ship with a piece of paper explaning the taxidrivers where to drive to in Japanese (my last pic)!