Really, it would help a bit if you explained when you'll be traveling, and what you are primarily interested in (i.e. culture, beaches, etc.) Portugal is an absolutely fabulous place with a wide range of scenery. I have most experience with the southern bit -- the Algarve. There, I would recommend the coastal towns on the western Atlantic coast, and forget the foreign colonies on the southern coast. Top recommendation would be a B&B called Das Dunas in the village of Carrapateira. (Tel. +351 282 973 118).
Recently, work has been bringing me to a city called Viseu in northern Portugal. It too is wonderful. A beautiful old town, great food and crisp blue skies.
If in northern Portugal, and if you need to clog your arteries with a taste of heaven, order the typical plate called the Francesinha.
Remember that Portugal is colder than Australia, and that your mother should remember to pack a jumper, even if traveling in August. Enjoy the trip.