Yes, there are hair dryers and depending on your hair, they should work fine. Just was on Jewel of the Seas and those hair dryers were great. If you have longer, thick hair, you may want to bring your own, but if not, save the packing space.
Just got back from Explorer of the Seas and they had one. We actually used theirs instead of ours because we liked it better. Ours was not located in the bathroom but in a drawer in the desk/vanity area.