The advantage of a bus, as is always the case when touring a new place, is the fact that you get to see the city as you travel around. So, though the bus is less efficient and at times more expensive, it remains an excellent option.

For further information try Porto's Bus Service Site: http://www.stcp.pt/en/home/principal.htm
Tel: 225-071-000
Blue Lines info: 808-200-166