I rode from Porto last year and had no issue getting my credential. If you start at the old cathedral in Porto, which is beautiful, you can walk part of the camino path through the warren of little alleys or ride the sometimes sketchy roadway out of town. I rode the streetcar tracks out of town and then along the coast. As
@t2andreo mentioned, it is safer and more enjoyable once you get to the north part of town.
There are a couple of knee challenging spots, which is to be expected, but nothing too long or difficult and there are alternate routes that you can take which might be more gentle.
I had no problem with lodging, by the way, other than when a festival came to town. And one of the benefits of cycling is that when all albergues or hotels are full, that additional 5K to the next spot is possible, even if difficult and unwelcome.
The downside of cycling it is that the experience is over too soon. Next time I'll start in Lisbon or Barcelona. More solitude and contemplation, please!
Do equip your bike with a bell and slow down and enjoy the journey. I didn't have any issues with walking pilgrims, but occasionally felt it best to ride a parallel road on the bike lane, especially after Tui.
Oh, and I recommend enjoying a pastel de Nata as often as possible. You leave Portugal far too quickly.
It is a beautiful route and may your pilgrimage be exactly what you need. Bom Caminho!
