When the ship is in port you shouldn't have a problem using your cell phone, but check your coverage area to make sure Hawaii is in your plan. I used mine the entire time I was on the trip, calling home to Georgia almost everyday. However, when the ship was traveling at night, it's far enough from shore that I couldn't get a signal.
Top 50 Contributor
Yes, but rates may be different. Refer to the following link for more details.
Top 10 Contributor