I stayed at Maria's private room for several days while I was visiting Santa Monica. It's a modest room as described in the listing, and while it has connecting doors to both the living room and a shared bathroom, both doors are lockable from the inside, allowing for a reasonable sense of privacy.
The check-in time was considerably later than I'm typically used to (8pm), so it did mean that I had to kill several hours before I could check in. The Santa Monica weather was beautiful so I enjoyed exploring, but your mileage may vary.
I did find the room rather cold, especially at night and in the mornings (my stay was in December), which meant I had to really bundle up overnight.
One plus I noticed was that the wifi was quite fast, if that's something that you need during your stay.
Overall, I had a good experience at Maria's.