Thought I would recomend my favourite hotel in Porto which is the Hotel Pennisular, Rua S6 Da Bandeira 21. telephone 222 003 012.
It is an old art deco hotel which oozes faded glamour and has a fantastic lift inside.
It is very conveniently located in the centre near the railway station and is very friendly, clean and good value at 22 euros, rising to 72 euro's for a double in high season (that does include breakfast and a bathroom)
Ask for a room at the front, they are a little more expensive but the rooms are bigger and brighter and have got antique furnishings.
Ther are loads of hotels in Porto so you shouldn't have any problems finding somewhere to stay once you arrive.
The Grande Hotel de Paris is on Rua de Fabrica, it is cheap and again art deco in it's decoration, It's nice but not as great as the Hotel Pennisular. If you require a number let me know.