Florence Robson, Aug 4th 2015, 09:21 Verified Guru
You can get a NIE for any area of Spain (for example, I got one for my year abroad in Madrid).
It's not absolutely essential for you to get a NIE if you're only in Spain for a year or less, but you need one to open a resident's bank account. If you're going to be employed by a Spanish company, it would be a good idea to get a NIE sorted.
Here are a few articles that talk through the process of getting a NIE! If you're off to be a language assistant, make sure you attend the orientation talk at the beginning of the year, as they'll set you up with a NIE appointment.
There's also a great answer to a similar question about the NIE elsewhere on TYA Answers.
Hope that helps :)