City Sightseeing - Casual clothing items like shorts, t-shirts, or sundresses are fine. Wear comfortable walking shoes, or your hiking boots if you’re looking to save space in your backpack or luggage and intend to do some hiking as well.
Beach days - If you’re planning on spending time on the coast or at any of the many beach towns bring a few swimsuits and coverups that dry quickly. You can easily spend two weeks there visiting a different gorgeous beach every day. Bring a nice dress or two for dinner dates.
Bar Crawls - Lisbon’s Bairro Alto district is known worldwide for its fun and crazy nightlife. Spend a night (or two...or three) getting to know the city through its famous sour cherry Ginjinha shots, but make sure to dress appropriately. Keep it classy, and don’t wear anything too revealing. A cute, flowy dress is great for women, and men should plan on wearing slacks, dress shoes, and a nice t-shirt or button-down.
Fine Dining - Portuguese food is to die for. Get lost walking down winding cobblestone streets, find a cozy corner restaurant, and take your time having a delicious, slow-paced meal. Bonus points if you find a hidden Fado house, and listen to the hauntingly beautiful voices and guitars of classically trained Fado musicians. Bring semi-formal clothing if you plan on dining out like this. A tie for men and some heels for women are definitely appropriate.