We had a very nice stay at Rui's place, even though we spent much of our time working from the apartment. It's very spacious, there's ample seating outside, and also a large dining room table if you are looking for a laptop friendly space. Note there is no door to the ensuite bathroom from the bedroom, so best for a single person or a couple who is used to this arrangement. Rui was very helpful and friendly and able to make recommendations for shops and places in the area. There are a number of great, inexpensive traditional Portuguese restaurants within 10 minutes walk. And the beautiful Palácio Nacional is at the top of the hill very close to the house.
Rui's place is up the hill from Belem, which may be difficult to get around on foot if you are not physically fit as the hills are quite steep. However, there are buses that go to the top and if you primarily travel by taxi then this is not a problem.