I researched Portugal a bit.
Check the weather in Faro, the Algarve region.
I have heard that the most English language city is Porto. But not a problem communicating in any city.
Really depends on what you want most from the trip. Miles or sights? Flat or mountains?
There is a BF member living in the Algarve region (well, probably more than one) that is a serious cyclist. Check forum names = Algarve-
something. In his area, excellent bike rentals are possible. Camping is possible in many areas, but that was not my direction. I was looking for a southern location with day rides and a northerly spot for same. Faro to Porto rail for xfer between 2 locations.
Google cycling in Portugal and go from there. I found an 'official' internet site showing cycling routes, distances and level of difficulty in the southern region. Everything from the southwest tip on the Atlantic to the Spanish border - coastal and inland routes. Maybe from a regional tourist agency. Quite useful. It had lots of links, but no pop-up ads (that's why I think it was a govt funded site). I assume such routes are fully documented for other regions in the country. I should have saved the link as a favorite.