Hi Robyn from Napier. I’m in Auckland if you want to chat….but to answer your question I cycled from Lisbon to Coimbra in early October. It’s flat and semi industrial heading out of Lisbon for the first 2 days, though the river is close, and the railway closer. Then it gets more interesting and hilly. I was doing 40-60k a day, and I took my time as I was on my own. The terrain changes frequently, tarmac, cobbles, gravel, farm and forestry roads…so in the couple of gnarly bits, where I had to unload the bike, push it uphill and go back down to retrieve bags ….it was very short lived….and I always enjoyed the downhill
I met loads of cyclists, road and mtb,….out for training or recreational rides….and didn’t see too many pilgrims walking….but there were a handful every day.
I can’t speak to after Coimbra, from what I’ve read, it is very hilly and potentially slow in poor weather. I was told to avoid the suburbs of Porto, them being the most industrialised parts of Lisbon….so I took a local train across to the coast. You can cycle from there on Eurovelo 1 to Porto…..much more pleasant.