Cascais is popular with Lisbon's upper-class families. Locals are mostly successful couples in their 50s who commute to Lisbon on a daily basis. The town's students are usually still in high school.
The beaches on the western side of Cascais - Guincho in particular. When the wind isn't blowing you away, Praia do Guincho is one of the country's best beaches, while also being fairly hidden.
Try the original Santini Ice Cream shop, next to the train station. It is said that their ice creams are the best in Portugal, so good that the've even opened a shop in Lisbon's centre and in Porto.
Life in Cascais is chilled. The seaside atmosphere mellows everyone's spirits, and when the sun is out, expect the beaches to be packed.