We need short stages because I am old so we started with 15 km or less. There is no question that we had urban walking and road walking but we saw that as part of our Caminho. Very different indeed than the
Camino Frances.
We used tricks like the first day we walked from the Cathedral, la Se de Lisboa, to the Park of Nations, just over 16 km and then we took the subway back to our hotel. The next day we took the subway to the park of nations and started there. And so on.
We walked good part of the way before May 13 so there were a lot of Portuguese pilgrims going to Fatima. They walked pretty fast and were well organized with support vehicles to carry their luggage, water, fruit that they freely shared with us. They told we had to wear reflective vest while on the road as per directives from the police and in fact one group had an extra vest and they gave it to me instructions to buy another at the next supermarket. The left us in Santarem, the caminos diverge there, but we still have the vests and we are bringing them along (I would recommend you buy vests for yourselves. They are very light and give us a extra degree of safety).
I would not change that camino. This time we are starting in Tomar because we both, me (knee) and Wonder Woman (elbow) had accidents that required surgery last year and we just wanted to shorten the distance. We have planned an itinerary that only has 2 days of 20 km, the rest of the days will be shorter.
My advice, do the whole from the cathedral of Lisboa to the cathedral of Santiago. And do visit Fatima. We took the morning bus from Tomar (very early) and came back that evening to Tomar, next day back to walking.
It was phisically easier than the Frances, the countryside is very different (no big mountains), there is only one reasonably longer hill, I think is just afterPonte de Lima. You will find many little hills but nothing like going up to O'Cebreiro.
If you want the gory details, I wrote a a blog:
http://gilcamino2.blogspot.ca/
Bom Caminho
Gil