Hi, Nadine,
I walked the VDLP in 2010 and took the Sanabres route, it's lovely. Mig is right about the way out of Ourense, it's steep. There are two options, one to the left, one to the right, very shortly after you cross the bridge leaving Ourense.
There are a couple of prior posts on the topic of which way to go out of Ourense, so I won't repeat what I said there:
camino-mozarabe-and-via-de-la-plata/topic10127.html
camino-mozarabe-and-via-de-la-plata/topic5714.html
As Mig said, there are no reservations in the municipal albergues. I spent a night in the Monastery of Oseira (a bit cold, but highly recommended!), which is about 8 or 10 kms beyond Cea, I think.
I was also on the final part of this camino last year when I walked the Camino de Invierno, so my information beyond Laxe is only a year out of date, rather than two.
I don't know the albergue in Silleda, but it's a big-ish town with cafes and grocery stores. The albergue in Ponte Ulla is actually not in Ponte Ulla, but about an hours' walk uphill to the hamlet of Outeiro. There is a chain grocery store on the way up and out of Ponte Ulla, where you can buy groceries. There is also a great bakery in town, right on the camino.
Outeiro doesn't have shops, but there is a restaurant about 1 1/2-2 km downhill where people go for dinner (the restaurant delivers as well!). There is also a fancy old estate turned into a rural hotel if you are looking for a splurge:
http://www.pazodegalegos.com/
I arrived early in Outeiro and walked down to look around, and I got a very nice tour, this is a beautiful place.
The albergue in Outeiro is very nice -- last year when I was there, they had just hired a new hospitalera who was taking great pride in keeping the place clean, which is a most welcome development! There are two big rooms, lots of showers, nice grassy areas, etc.
I think you'll enjoy this route a lot, there is a lot of beautiful rural walking. Buen camino, Laurie