Elis apartment is about 2km from the very centre of Porto. If you reach the river, the walk is really nice and beautiful. Elis' mum took care of us and prepared our breakfast every morning (we had granola, ham, cheese, jam, banana, more than we needed). Though she couldn't speak english, she made sure our stay was perfect, she gave us some extra towels and beach mattresses when we needed some, the bathroom and the shared areas were always perfectly cleaned.
Our recommendation is : go and stay with Elis' family! You won't regret it and you will remember their kindness forever.