You might have a solution with our partner on Expat-Quote for calls and data abroad. Have a look and give a try if this is convenient.

The best option might be to purchase a prepaid sim when you land at the airport. You can put €20 on it at the beginning for example and see how it goes. In Portugal prices will be €20-30 on most pay-as-u-go plans anyway.
You can get a PAYG micro-sim with http://www.yoigo.com/