From the FAQ section on www.carnival.com. I haven't been on the Valor but Carnival says it has hair dryers in the rooms.
Do I need to pack my Hair Dryer?
A hair dryer is provided in the bathroom (Destiny, Triumph, Victory) or at the desk/vanity in the stateroom (Spirit, Pride, Legend, Conquest, Glory, Miracle, Valor, Liberty). Hair dryers are not provided in the staterooms of all other ships.
Yep, we sailed on the Valor in an inside, and yes there are hairdryers installed in the vanity drawer,,,,however,,,,they aren't very powerful,,,,and you have to hold the "on" button in to make it work. Kind of a pain. If you have a small travel hairdryer, I'd suggest packing it. I think you'll thank me when you return.
Have a great cruise.