SoCal says the same - a bunch of busy corridors where VFR traffic don't need to be talking go right through approaches and departires for busy airports. I know the redesign of the SFO Class B created some huge holes where you don't need to be talking to anyone. Creates some major conflicts, particularly with OAK and HWD arrivals.
I've done a lot of flying in SoCal sky. There are many areas where the Controllers don't want you balling up the frequency. Some are by design such as the SFRA over LAX. And the VFR Corridor over SAN. It's right on the Chart and it says "...no communications or clearances with ATC are required..." and then tells you what frequency you should be on "...frequency 126.050 is provided for exchange of information between those pilots using the corridor..." When using the Practice Areas the 'unwritten' custom is to use 122.75 to exchange traffic info. The CFI's know about and use it. They have it broken into areas such as Coastal, North, East etc. I found this while doing a search to refresh my memory:
[Being a student pilot in San Diego, I use 122.75 every time I fly.
It is used in regions such as: San Diego Coastal, San Diego East, and San Diego North.
Yes, it is true that we use it to announce aerobatic intentions, but it goes beyond that. It also is not exclusively for fixed-wing aircraft, because both fixed-wing and rotor craft need to know each others intentions.
VFR traffic generally uses it to let other aircraft know what their intentions are. ex: "San Diego Coastal, Cessna 739MH, over Del Mar 3,500ft northbound, San Diego Coastal." or, "San Diego East, Piper Warrior 223F, over El Cap 5,700ft stalls, San Diego East."
If there is another aircraft in the vicinity, and they heard the transmission, they will respond with their information, and coordinate with the pilot to ensure they remain clear of each other.
Sometimes, you may hear chit-chat between pilots, but most are kind enough not to hog the frequency or step on other pilots. You will also hear pilots who are flying in formation using this to communicate with each other.]
One place they are always begging us to call them up is in the area along final to KSAN.