That is why I stay at hostels. It is most disappointing when you strike one where there really is not a 'hostel atmosphere'.
I can highly recommend the USA hostels, especially the one on Schrader in LA. I stay there everytime I am in LA. Secure, clean and comfortable. Lots of activities and a vibrant atmosphere. If staying for several nights (can't remember how many), they refund part of your shuttle cost from LAX. It is in a great part of town, and even as a senior female travelling alone, I have never felt intimidated walking the streets, both day and night. Not far from the subway and busses. Sundays there is a Farmers market only about four or five blocks to the east.... Ivar St, from memory. Park overnight across the road in a secure facility for (I think) $10. And the Gay and Lesbian Coalition is across the road. I am sure you wanted to know that. LOL
Book early... I have once missed out.
I have not stayed in their San Francisco hostel, and stayed twice in the one in Las Vegas. That one is OK, but not as great as LA, and not in a good part of town. Upside is that they do have a swimming pool and secure parking.
And just a little off the topic... but relevant. If you are members of the NRMA make sure you take your membership with you. This will give you
free access to all tourist information and needs from the AAA, such as detailed maps of the State and of Urban areas, as well as road information and trip ticks if desired.