Louise
Its a very nice and easy 501km round trip to Granada which we recently done. I strongly recommend that you pre book on line for the Alhambra Palace as it gets extremely busy and does sell out.
We booked a Hotel in Granada for one night which enabled us to enjoy a more leisurely two days. If you obtain tickets for the palace you will have time slots therefore you may need to be there early which makes an overnight stay necessary.
I also recommend that you take the scenic round trip, we took the 340 via Sorbas through to the A92 stopping at Guadix where we paid the cave house museum a visit. We left Granada via the E902, where there was some spectacular scenery, down to Motril and returned to Thalassa via the coast road E15.
All in it was a trip well worth doing and one that we will definately do again, GO FOR IT, YOU WONT BE SORRY.