To obtain a Portuguese passport you must be Portuguese. Having family members (grandmother or father as it seems to be the case) won't grant you the access to the document. In fact I'm wondering if what you wish is a Passport or Nationality... You can only have Portuguese passport or nationality if you have a Portuguese birth certificate, otherwise it won't be possible. The cost can reach 200 USD or more, but that will depend in the urgency and other applicable fees, If you're portuguese and your grandmother or your father are in Portugal you'll have to write down a special document where you enable all legal permits to the person that will act in your behalf. I hope it helps though it's been a while since you posted the question!