Hi Lisa, I'm from Ireland and also trying to move to spain to work as a nurse, I have already validated my license and am just looking for a job now. To validate your license you need to get in touch with "departmento de homologación y reconocemiento de títulos" in the ministerio de sanidad in Madrid, and to validate your license, you'll need a copy of your degree and official translation, copy of your american license and official translation, and a copy of your passport or DNI if you have one. It's better to in in person and hand in the documents, but if you're sending them by post, make sure the copies of your originals are convalidated by the spanish embassy, they won't accept photocopies convalidated by the police.
They got back to me pretty quickly, I got my license within a couple of weeks.
Getting a job is another issue, I've just entered into the "bolsa" to get a job in Madrid, there's a different one I think for every city, depends where you want to work, to get a job in the public health system, which is apparantly next to impossible. Still haven't heard anything from them, am looking at private hospitals now trying to find something.
Would love to hear how you get on, if you get any information about getting a job in Spain I would love to hear about it!