Hiya. I'm not sure if you intend to walk the central or coastal route. I have done nearly all these routes on more than one occasion. I do believe your initial question was with regard to communal dinner at the beginning and if not then en route. I've yet to find a communal dinner in any of the albergues in or around Porto except one at the far side of the airport in Mosteiro which I do not recommend. Food etc was fine but the prices were deceiving and not pilgrim friendly(I'm not being a cheap skate
) However I would suggest maybe stay at Senhora de hora or somewhere like that and cook up pasta with bread, wine and cheese and create your own communal dinner. Anytime I've done this I have found it a great way to meet and chat with other pilgrims. Generosity, kindness and love is I believe the true heart of the Camino and many a pilgrim will be drawn to this.
As many have said Ninho(Rubiaes) and Casa Fernada are amazing places to stay and experience joy although do please book them ahead. All that been said some of my favourite meals were on top of a hillside somewhere beside waterfalls or a steam with nothing but the ingredients of my last supermercado trip.
Have a wonderful Camino, may the road rise to meet you and "your' God be with you every step of the way. Daniel. P.s We are walking the Mozarbe from Almeria in September so may send you a smoke signal