If you want a occasional solution that gives you unlimited traffic, for approximately the same price, you can also hire an Wifi hotspot.
There is a company that does that specific service. They are called Portugal Internet, and you can find them at http://www.portugalinternet.com

There is now a company in Portugal that rents Wifi hotspots, and sells prepaid data SIM cards, specifically to tourists and non-Portuguese residents, that don't require any contract. Traffic options goes from 1GB to unlimited. They are called Portugal Internet, and you can find them at http://www.po...