We stayed at Cathryn's apartment in september 13. Is is a really nice apartment and Cathryn herself is a very nice person so no problem at all at having a room in her apartment.
You can move by taxi or like we did by catching the 19 bus that stops just 2-3 minutes from the house..walking to the center takes a little too much time.. the only catch with the bus is when you return home at late night. San Francisco has many homeless (and crazy) people going around in downtown so obviously you will find them on the bus too.. but if you do not get scared to easily it is OK. Just sit in the front seats near the driver :)

The neighborhood around the apartment is excellent and very very safe, no crazy people there! Also there are some nice places to eat at walking distance, so eventually you can stay there at night too.