If it helps with your planning, October is generally a lovely month to visit Portugal, but—as others mentioned—you should expect some rain, especially from mid-October onward. Temperatures usually stay mild, and the advantage is that the big attractions are less crowded than in summer.
Your Lisbon → Nazaré → Fátima → Porto route is very straightforward. Nazaré is great for coastal views, and Fátima is easy to visit even with just a short stop unless you're planning something more in-depth.
When you reach Porto, one thing that really helps is getting a sense of the layout early on — the historic centre is beautiful but quite hilly, and having some local context makes the rest of your stay much smoother. I found this Porto visitor guide particularly helpful for planning what to see and how to organise the days: https://bluedragon.pt/category/porto-tourist-guide/
It’s written by a local team and gives a good overview of neighbourhoods, viewpoints, and cultural highlights.
For hotels, everything depends on your budget, but in Lisbon areas like Baixa/Chiado or Avenida da Liberdade are very convenient. In Porto, Ribeira is charming (though touristy), while Cedofeita and Aliados offer easy access without the crowds.
Regarding flights, business-class fares from Madrid or Barcelona can sometimes be much lower than from North America directly into Portugal, even when adding a separate connection — worth checking if your schedule is flexible.
Hope this helps with your 2026 planning!