Hi Tom: I will be cycling the Caminho Portugues from Lisbon beginning September 4th. I have decided to rent a mountain bike with front suspension from BikeIberia
http://www.bikeiberia.com/. There is a very helpful English speaking lady named Tania there. You can send her an e-mail as well. I learned about BikeIberia from an Australian couple who are on this Forum: Heather and Gerry. They also have a great blog that I would highly recommend.
BikeIberia also conducts Lisbon sightseeing via bicycles. I will take advantage of this offering as I want to see Lisbon (never been there).
You do not state where you are from. I am coming from the NYC area for this Camnio. I have done a bit of research so if you have questions on routes, etc. I will be glad to share.
Buen Camino,
John