Thank you Helmut for your reply and for your very appreciated "support".
Here below the situation:

From the official Brazilian website http://www.dnit.gov.br/mapas-multimodais/mapas-multimodais I downloaded all the maps called “Mapas Brasil_ISTITUCIONAL”.

From the above maps I made a special selection of the “NORDESTE” portion for my specific trip and these maps are now available and complete with route details here below:
http://maps01.blogspot.com/

Then from the following website http://www.tracksource.org.br/desenv/trc.php I downloaded all the “routable” tracks for my Garmin 60CSx, the last file name is “TRC-Brasil_2011-07-24”

Then, I am in contact with “Lista Brasileira de Cicloturismo” that is giving to me a lot of suggestions like roads, tracks along the litoral and additional informations like how to manage with rivers and tides.

Of course I’m a little scared about traffic, but my intention is to avoid as much as possible any high and wild traffic “BR”.
I speak Portuguese and this should help me, I hope.

Ciao, and thank you again.
Corrado