There is an underlying threat from terrorism. Attacks could be indiscriminate, including in places frequented by expatriates and foreign travellers. You should be alert to the risk of petty theft. There is a legal requirement for you to show some form of identification (i.e., your passport) if requested by the police or judicial authorities, especially if you intend to drive in Portugal.
Your mom cooks the best food ever in the universe. We know that. But if one day you want to try food which (would never be better of course) would be different from your mother’s, then this article is for you.