2 nights in Granada - most efficient trip?

Well, some do slow travel and some take the 'tapas' (taster) tour. I spent 4 nights there and didn't visit the Relajo district at all, so 'must see' means different things. Depends what your interests are, but a lot of Rick Steves posters seem to prefer the 'tapas' approach. If you think you will get saturated by cathedrals and old buildings, then move on in the morning. You will have better cathedrals and old buildings in Seville.

You are going to Granada to see and experience the Alhambra, so I suggest you visit more than once. Go up on the afternoon you arrive, and walk around, visiting the open ( non-ticketed) areas to get a sense of the layout. Have dinner on the terrace (the casual restaurant) of the parador.

Or, do the night time Alhambra visit - rather fantastical and the stucco work details show more with the shadows from the lighting. It can be rather flat during daylight. I see now you are traveling in March, so you will need to book asap for any visits to the alhambra. A night visit to the palace tends to be shortly after dark, so 6 or 7 pm.

Late afternoon arrival - walk around theAlbayzin, aim for mirador San Nicholas at sunset, eat with a view of the Alhambra (there are plenty of places near San Nicholas, or downhill on carrerra Del darro)

Alhambra, then maybe the cathedral and royal chapel that afternoon, if you finish the Alhambra in time.

I would also suggest walking around the Alhambra in the evening before your visit. The only tickets you need are for the Palace and the Generalife but the outside can be explored on your own. Then the next day you have more time to visit the ticketed areas.

I enjoyed walking around the Sacramonte even more than the Albacin. The views of the Alhambra are beautiful from there and the neighborhood is really quirky/interesting

We'll be getting into Granada around 4 or 5pm. We'll be staying near Plaza Pasiegas. Sadly the night tours of the Alhambra won't open till after we leave. Thanks to everyone for the great suggestions!

I understand you will be there in March. Sunset's around 7.15-7.30. You could go up through the Albaycin to Mirador San Nicolás for the sunset views then work your way back down and stop for dinner. It's quite steep, so you may want to take the minibus or a taxi up. While the streets are a maze, as long as you're going downhill, you can't get really lost. Allow a lot of time for the Alhambra, the campus is very big and there's a lot to see.