Our current itinerary would have us spending a Sunday in the Douro Valley. Will most things (wineries, Quintas) be open on Sunday?
I went on a Sunday last June. I went on a day tour from Porto that visited wineries, included a boat ride and a restaurant lunch. There were also independent visitors at these places which were definitely open. When we stopped in the town of Pinhao, some of the shops were closed because it was a Sunday but there were still some places open where you could buy coffee, a snack or souvenirs.