Obviously depends on where you are going. The northern regions, Madrid, Aragon, Catalonia, La Mancha etc, seem to be getting most of it. Same as some parts of Valencia but south of Alicante not so much.
Just as safe here as anywhere I would say. Try to avoid large crowds if possible, the face masks are annoying but, to be honest, after 10 minutes or so you seem to get used to them. Big towns seem quite busy but the smaller ones are pretty empty at the moment.
The bars are also closed now until the 21st September. Only those places licenced to sell food are open which means you can just go there for a drink, Masks to be worn whenever you get up from the table, like going to the loo etc.
Do you have to quarantine in Ireland as well? That and going through the airports would be the annoying thing for me.
The number of cases are shooting up in Spain but that could possibly due to the fact they are testing so many and loads who wouldn't have shown symptoms are now being classed as positive.
So, is it safe? As said, as safe as anywhere I should think. Life appears normal except for the face masks and hand washing when entering anywhere. Much quieter than usual in most places but wear the face mask, wash your hands regularly, keep your distance and avoid crowds. Chances are very low you'd catch anything but take precautions.