Albergue sleeping equipment...

Hi,
I would think it'll be a bit cold in march, I would take a sleeping bag with you rather than just a liner. On the portugese side the accomodation is mixed but I think most had pillows and sometimes extra blankets. Once in Galicia all the albergues give you standard issue Galician cover sheet and pillowcase (so there'll also be a pillow!) and there'll probably be blankets.
It depends how cold a person you are, I saw some folks in may doing it without any bedding at all just sleeping in their clothes but like I say I'd advise a sleeping bag. Some of the albergues are pretty old stone buildings and can get a bit chilly!
Buen Camino and have fun it's a lovely route!

Oh also i's much quieter than the Frances you won't need a sleeping mat!