Aye, you have a problem there, lassie!
There are very few english or scots speaking expats here in Portugal who actually speak Portuguese. I do!
A large part of the problem is down to arrogance and the complete unwillingness of of english speaking expats when living in foreign parts to immerse themselves in the local culture.
You may have a better chance with a Portuguese family, However, they will probably want to speak english to you to improve their English!!!!!
Some tips:
1) Avoid the Algarve like the plague!!!!!!!! English is the second laguage here !!!!!
2) Also avoid Cascais and Estoril in the Lisbon for a similar reason.
3) I would recommend one of the cities like Porto, Coimbra, Braga or Guimarães.
These are student towns and you may find that as the university year winds down, reasonable prices accommodation will become available.
Have a look at this site:
http://rentals.expatsportugal.com/
Also register with this site and post your requirement there:
http://www.expatsportugal.com
There will be a lot of non-portuguese speaking expats there but you may be lucky and find a housing sitting requirement.
There are websites/forums with classified listings in portuguese but if you are not confident in the language be careful.
There is one for rooms and shares at this link:
http://bit.ly/olxportugalrentals
