There are many hotels around the center of Naha city.
It takes approximately 30 minutes (10 km) and costs average \3,000 from the center of Naha city to Okinawa Convention Center by taxi.
We recommend you to book a taxi at your hotel, when you would take a taxi in the morning.

Please refer hotels around the center of Naha city:
http://travel.rakuten.com/hotel/asia/japan/okinawa/index.html