<http://kpbs.media.clients.ellingtoncms.com/news/documents/2011/01/28/fire_agencies_phasing_STEP2.pdf>
This map is the best that I have found so far for the rural areas. You can see that some stations are bunched together - but there are also large areas of mountains and desert that dont show up on this map.
There have been many changes over the last couple of years regarding these stations. If I understand everything correctly, all of these stations are now staffed year round by a minimum of 3 people - except maybe - LaJolla Tribal + Mesa Grande Tribal + Santa Ysabel Tribal - those areas have very few buildings or people.
The Forest Service stations are typically staffed daytimes by 1 or 2 Type 3 wildland engines (150 GPM / 500 gallons) with a crew of 5. These USFS stations are staffed at night if there is a wildland fire reported, The crews have to drive to the stations from their homes I believe - or maybe some stations have bunkhouses to house crewmembers overnight.
Warner Springs Ranch used to have a VFD. But a Indian tribe bought the place in 2009, and apparently the VFD went out of service. So the nearby CDF station was given a County Engine and a County water carrier apparently - and some fulltime firefighters to staff them.
SDR = San Diego Rural
All of these rural "volunteer" stations have now been merged into the County Fire Authority. Therefore the VFDs go out of the fund raising business - and get fulltime staffing - and new pumpers and water carriers.