I have received a traffic fine from when I was in Granada.
My details have been passed to the police by the car hire company.

Will I have to pay the fine?

Can I just ignore this letter and cancel my credit card?

In the future.

Don't ever go past one of these signs in Granada. 

There may not be a physical barrier but don't go past. 

It will create more problem than it is worth.  

 

The hire company sometimes charge an 'admin' fee of around 25 euros on top of the fine.
If you don't pay the fine you will not be able to hire a car with the same company again.

You can only easily avoid paying if you are not a Spanish resident.
If you are a resident they may be able to "embargar" your bank account.

If you are not a Spanish resident then it is easier not to pay.
To avoid paying you will have to cancel your card, however this  may be inconvenient.
Once the money has gone out it may be hard to reclaim especially as the offense will be documented with photos so if you are going down that route it may be best to block your card straight away.

Some time in the future when you come into Spain the fine may get flagged up on a computer.

The best thing to do is not get a fine in the first place.
Apparently Granada council earn over 30 000 euros per day in traffic fines.

They used to have physical barriers and people would go over them and smash them.

They learned that it is much more profitable to take photos of your numberplate and get fines. 

If you see any big yellow sign in Granada with the word "prohibido" on it don't go down that street.

By the way:  the Guardia Civil set up many radar traps in order to earn extra income from speeding motorists so when in Spain always drive within the speed limit.  Especially when the speed goes down from 80 to 60 around traffic junctions.

For more info about driving in Spain visit this page
https://granadainfo.com/driving-spain.htm

This page has driving distances from other cities to Granada
https://granadainfo.com/distances.htm