I made reservations for the Alhambra online through ServiCaixa and the confirmation pages states I need to bring the credit card used as well as an "official identification document." Do I need to bring my passport or is my US drivers license with photo okay?

I went to the Alhambra last April. It seems like I needed my confirmation number and credit card. I didn't have my passport with me that day (although I did have my US driver's license) To be on the safe side, you could bring a copy of the passport. It sounds like from some of the other posts that is necessary. The last few times I traveled in Spain, I didn't carry id with me most of the time, but from what I've read, maybe it's important.

Enjoy the Alhambra. It is magnificent. What time of year are you going?

Next week! Not the best time of the year, but it was the only weekend that worked with my sister's study abroad schedule (um, free room and board!) and my work schedule. I will be in Madrid most of the time, but decided to take a weekend trip down to see Cordoba and Granada - I figured going to Spain without seeing the Mezquita in Cordoba or the Alhambra was like going to Italy and not seeing the coliseum or the Sistine chapel.

Have fun, you'll love it...Make sure to go to the look out across the way to see the sun set over the Alhambra...Anyone can tell you where it is, it's a very popular spot. Enjoy!!!!

Teachertraveler8 .. ID can be be necessary here . For example , I went to the Valle de los Caidos to see Franco´s mausoleum . Whatever you think about him ( I disliked him ) , the setting is amazing . Believe me , Amazing ! BUT you have to have ID with you . I went with MM , a Spanish friend who was kind enough to drive us and his friend from Denmark . When we got to the entrance in the mountains , my lack of ID was an issue ! Eventually my friend Rafa told the guy I was from London .. I was wearing and England rugby hat and a London sweatshirt .. the guard smiled and shrugged his shoulders and let me through . !Viva España !
Oh and remember , for La Alhambra , you must book in advance . And please go to a bar in Albaicín in the evening and have a glass of wine looking up La Alhambra all lit up . It´s a magic moment !

Steve your (I disliked him ) put the Peter Cook and Dudley Moore sketch, when he says I was completely against it.
Not having a go or anything its just what came into my mind

yep you have to have id with you at all time, its the law as in France. If you dont have an ID, make a copy of your passport,never give the original out, keep it in a safe in your hotel or home.
and yes to go into the places even sports music events you buy they will ask for the credit/debit card you use to purchase it; you need to show it or swipe on a machine and it print your tickets, I do all the time in Spain, just came back from Madrid and the tickets to Bernabeu got them like that although at socio rates hehehehe
Enjoy the Alhambra one of the best wonders of our world !