Thumbs up! Cecilia is a super host and the room is very nice.
The room is spacious and clean; it has a drip coffee maker and a (not so) small fridge wich was full of stuff when I arrived: nice touch!
The cat around the house is quiet and clean, despite hers astonishing resemblance to Garfield, she won't bother you.
The acces to the room is almost independent and you will have complete privacy. On the other end Cecilia might invite you for breakfast or dinner upstairs; we ended up having a brunch together. Another nice touch.
The neighbourhood is lively but quiet, relatively well connected to everything via buses. Nightlife in the mission is within walking distance.
Shops, restaurants and cafes can be reached in a few minutes on coortland. There is a farmers market close by.

If you decide to stay there keep in mind two things:
1) The house is in a very hilly neighbourhood: comfortable shoes a must, do not even consider smart shoes. Buses connect the place to anywhere however. Consider travelling light anyway.
With some coordination Cecilia will pick you up at the bart station and bring you back there when you leave.
2) [Only for the very coldish people] There is no heating. San Francisco can be relatively cold at night. No big deal, but you might have to plan your showers not so early in the morning or before dark.

My stay at Cecilia's was great and I would recommend this accommodation to anybody.