Under 50 eur is dificult to find a nice hotel, probably you will get no better than a 2* hotel, and most of those 2* hotels are horrible!! If are willing to pay 60 eur you will find a very nice choice: Hotel Tryp Porto Centro (http://www.maisturismo.pt/4/2194.html). Look into the www.booking.com

Have a nice trip

Thanks so much for you help Ricky_Moralez. how about Residencial Bela Star and Hotel America? Any thoughts about them? Btw, is something special happening that weekend (Oct. 5,6,7) in Porto? It seems that many hotels are booked that weekend or offering higher prices for that weekend.

Archifille, I don’t know either Residencial Bela Star or Hotel America, the only thing I can tell you is that the location of Hotel America is right in the heart of Oporto, in centre I mean, in a well-known commercial street and near to the Douro river and Ribeira.

And yes... you are right, 5 of October is a National Holiday here in Portugal, it is the day of the establishment of the Republic here in Portugal (began in 5 of October 1910), so it´s normal the hotel are full :))

Thanks again Ricky. Can't wait to explore Portugal!!!!

Check Grande Hotel de Paris.

Great value for money and is perfectly located.

Have fun!