You're paying for the location with this one. Walking distance to Petco Park, Gaslamp, and even Balboa Park if you don't mind a 20 minute walk partially uphill.
The room is small. Don't go in expecting a standard hotel room size. More of a dorm/hostel vibe. That being said, it's a perfectly fine place to sleep, shower, and rest in between city adventures.
John is very responsive and seems like he has a lot of experience renting out these rooms.
We'll probably splurge a little more the next time we come to San Diego and stay in Little Italy or one of the hotels, but this is a great booking if you plan on spending most of your time out and about and just need a clean, safe place to rest.