The appartement of Luis is perfect for few days and I could imagine to stay longer in this app if necessary. It contens free wifi, a small tv, a bar table, a complet kitchen, and the bathroom has a hairdryer and towels.
The appartement is just a 2min walk from Sao Bento Metro station and the center of the city. There is a small supermarket within few meters. And the rua de Flores has a lot of restaurants and cafes.
Everything in Porto is realy close, colser than you might think, and the most populare sightseeing points can be reached within walking distance from the appartement. Just next to the front door is a tourist info which rent bicyles and sell tours.