Good to discuss this with you again.
Hey RG,
I'll try to explain in detail and not be too tedious.

Kenji also PM'd me about some of this. Deep breath... Here goes:
When you go through the arched double doors through the porch from the drive way, you enter the open-ended room called a zaguan in Spanish architecture. In the zaguan there is a small door to the right before you go up the three steps to the arched loggia, along the courtyard, and to the stair hall entrance. That small door leads to the service wing as stated in RG's articles. That wing stretches back to the garage wing and is perpendicular to it. Also, on the opposing wall of the zaguan is a door to a trunk room as Rick Romer explained in his blog.
That small door leads to all the service rooms, the first of which, I believe, is a service stair in a U-shape around a dumbwaiter leading down to the basement, up three steps to the butler's pantry at the level of the rest of the first floor, and on up to the second floor. The butler's pantry is the next room back and it opens to three other rooms. Left is to the dining room adjacent the stair hall, straight back is to the main kitchen, and to the right is the servant's dining room. Following RG?

From the outside of the house, the servant's dining room has the three windows under the balcony facing the driveway. The main kitchen would be the two windows further right along the driveway toward the garage. The kitchen and other service rooms are only one story with a terrace above. Interestingly, as the building turns 90 degrees and becomes the garage, the adjacent part of the gable-roofed garage wing is service space connecting to the kitchen. The property tax drawings show this. I think this area has pantry storage, the laundry, and the second stairs to the basement I previously discussed.
Returning to the main kitchen, heading further back in the wing, is a servant powder room, access to the pantry mentioned above, and on to the service porch, or what might have been the cold-storage room. The service porch and adjacent laundry both lead to a rear service yard which is located between the rear driveway behind the garage wing, and the rear courtyard of the main house. That courtyard has the bath house. There are four windows with plaster vents facing this courtyard, two from the kitchen, one from the powder room, and one slightly lower at the service porch. These vent windows can be seen in the Magnum episode Distant Relative, I think at the beginning. These rear yard spaces are also shown in the land plat RG found from the time of the sale.
As for where the service stair leads upstairs, Sam, they open to the room over the zaguan. From the outside, that would be the room to the right of the large upstairs balcony over the arches. It has a window facing forward toward the front courtyard and one facing the driveway. I believe this is also the sewing room mentioned in RG's articles. It also mentions a linen closet which is one of the doors at the other end of the upstairs balcony, past the stair hall.
The balcony you mentioned overlooking the driveway is part of one of the three upstairs suites, and the only one on that side of the stair hall. It stretches linearly along the back of the house and includes a bedroom, sitting room, dressing room with closet, and bathroom. It also opens to the terrace over the kitchen and has another balcony facing the rear courtyard. A similar suite is on the ocean side but the rooms are not all in a line. Rather, the sitting room with balcony, and bedroom with rear terrace, face the water, while the dressing room and bathroom have windows overlooking the large balcony and rear courtyard, respectively. It's the one seen in H5-O a couple of times and the dressing room is in the realtor photos. The final suite between them doesn't have the sitting room, but has everything else including a balcony also facing the rear courtyard. RG's articles state this about no sitting room.
Whew!!!!! That's pretty close to tedious...
