Is There An Exception To The 3 Months Registering As Resident Rule?

Yes there is, this applies to jobseekers who can stay for six months without registering as residents.
Sample story

Marta is Portuguese and moved to Spain four months ago to try to find a job there. At present, she is living at a friend’s house. The Spanish police asked her to register her residence at the town hall, and to prove she had sufficient means to support herself while in Spain.

In fact, as a jobseeker, Marta is entitled to stay in Spain for at least 6 months without having to register her residence there. She only has to prove that she is a jobseeker who is actively looking for a job. The Spanish authorities cannot require her to demonstrate she can support herself financially.

Please note: The information provided is based upon our understanding of current legislation. It is not legal advice but is provided freely to enable you to be properly informed. We recommend that if you are considering taking action, you should seek professional advice.