Hello Paul,
I walked that route in August, 2008. I left Santiago quite late as I was seeing off some friends before I hit off on the Camino. From Santiago to Negreira is 21.3 km. according to my map. It was a lovely walk and didn't seem to hot even though I walked through the heat of the day since, as I mentioned, I didn't leave Santiago until nearly noon.
One point about Negreira. The albergue is about 1km beyond town. You must go all the way through Negreira, past the Chapel of San Mauro and the fortress, Pazo de O Cotón and then on up the hill to the albergue. When I arrived it was completo. I had met another peregrino and we returned to the town and stayed in the Inn on the main street on the left as you enter the town. They had a Pilgrim's Deal - something like €30 for a double room with twin beds including breakfast.
Negreira to Olveiroa (33.2 km) was quite hilly and walking on a high ridge. The scenery was beautifull, but I found there was a good bit of road (albeit quiet road) walking. There was a nice albergue in Olveiroa with some spectacular horreos. If you decide to stay in Olveiroa, consider dining in the restaurant Os Pios (I think that is the name - I mentioned it in another thread in this section) I believe the Pilgrim menu was €12 and it was one of the best meals I've had in a very long time!
When I left Olveiroa in the early morning, it was raining and deeply foggy. I was walking beside a deep gorge with a swiftly flowing river - I could hear it, but I could not see it. It was very eerie - the rocks on the path were a dark green! At first I thought my eyes were playing tricks on me, but sure enough, I picked one up for further inspection later, and it was definitely dark green! When I arrived at Hospital, I took the route to Muxía, but you can go on in the direction of Fisterra. I was told (and have read here) that the albergue at Corcubión is one of the best on the Caminos. From Olveiroa to Fisterra is 30 km.
If you are interested in seeing the photos from my trip, the link to my web album is posted in the "photos and blogs" section of this thread.
Buen Camino,