I did Lisbon and the Algarve (2 wks) with teens a few years ago. We only visited the beach once while in Algarve. We stayed in Albufeira but if I went back, I'd stay in one of the smaller towns (Lagos, Burgau, Carvoeiro). It's also easy to do a few days in Lisbon and a few days in the Cascais area. From there you can easily access Sintra and Estoril (which has a supercool outdoor evening market with food stalls, vintage stuff, new stuff, clothing, jewelry, etc. and music in the Jardim). We absolutely loved Portugal and would go back every year. Also would choose the beaches there over Bethany, etc. any day.
