You do not have to pay much for transportation once you're in the small town of Porto. Walk! You'll find so much more pleasures. Alternatively, get the day pass for zone 4, you'll save alot :)

This is a great seacliff in and the villages below are great to visit. Also its great to drive around there.

Take a local train from Lisbon to Sintra. It's easy and very affordable.
The main attractions are the Royal Palace of Sintra, the Moorish Castle and the Palacio de Pena. Especially the last one offers architecturally outrageous experiences. :)
The easiest way to get around is to take the palace tour by bus from the Sintra railway station.
Definitely, bring a camera with you. Also, it's not a bad idea to have clothing according to the weather conditions and very good walking shoes.

They have a wonderful user friendly metro system

Take a boat trip down the river of Douro, you will be amazed with the landscapes!

one of the nices relaxing places i have been to in awhile, wanna be back there

mini golf all day wit ur friends is fun, but just take breaks every few holes ok

You can purchase a day travel card from the metro station which gives you access to the metro, buses and trams for 24 hours. It only costs about 4 euros so definitely worth it if your going to be travelling round the city!

Spend a day to travel by boat to Farol Island. You can pick the boat in Olhão, 9 Kms from Faro. Ask in the reception of your hotel for the boat schedules. Enjoy the travel to Farol, seeing the Ria Formosa lagoon, Bird wathers will love it.

Make a deal with a local taxi driver. It's far the greatest and cheapest way to get to know all the corners of Madeira.