The dryers will most likely not dry your clothes in 1 cycle. You can put in "2" sets of quarters at one time. While it has been a couple of months sinced we were on the ship, I think that "1" set of quarters got about 40 minutes of drying time.
I would definitely recommend going early in the morning, especially if it is a "sea day" as the laundry room does get busy.
If you do the "2" sets of quarters trick - you should have plenty of time to go get breakfast etc. while you wait for your clothes to dry.
I apologize for the vagueness of my "sets of quarter". I think that each load, both washing & drying is $1.00 each.
There is a change machine in the room, but I would recommend just bringing your own quarters. Also, if you can, bring your own soap, as sometimes the ships run out of it in their vending machines.