If you are an EU national living in another EU country, you have the right to vote and to stand as a candidate in municipal and European Parliament elections held in that country. The conditions are the same for you as for nationals.
Bottom line? if you live in Portugal you have the same voting rights as a Portuguese citizen (Municipal / EU election process ONLY - NOT FOR NATIONAL ELECTIONS)
European Union citizens can vote and stand for election in local elections immediately after arriving in Portugal. No minimum period of residence is required.
A residency document and proof of address are required to register on the electoral roll. Inscriptions must take place at least 60 days before an election. Electors will be enrolled on the electoral list of their parish (Freguesia), at the address which is indicated on the residence permit. You can get a resident permit at your local municipality, or at SEF.
Voting takes place within designated venues at the local Junta de Freguesia (Parish), which is a sub division of the local municipality.
EU citizens can stand for election and be elected to any local authority body, provided that they have not been debarred in their country of origin from the right to vote or to be elected.
Should there be any doubt about this last point, the competent court may require the competent authorities of the country of origin to testify that the candidate has not been debarred from the right to be elected in that country, or that the authorities in question are not aware of any such impediment.