I stayed at Karl's place for a week to explore SD solo for my bday and am grateful for the find! I didn't run into Karl much as he was out of town for some of my stay; when he was around he was respectful and kind, setting up the sofa bed for my best friend who stayed a night.
The space is clutter free and well-situated. If you're hoping to walk to the ocean, this is the spot! Restaurants are within walking distance (along Cass or Garnet). It was central for drives elsewhere too, to La Jolla, Ocean Beach, Sunset Cliffs, Torrey Pines, Balboa Park, downtown, you name it. Oh and it's so quiet--my NYC brain appreciated it :-)