Check out the guest house with the private pool at Victoria House. It has a *huge* kitchen and entertainment area, an incredible master bedroom (upper level), a couple of baths and I think another bedroom in the main part of the house. On the upper level, attached are 3 or 4 LARGE bedrooms with private baths, on a common deck. These bedrooms can all access the main part of the house but have private lockable entrances. If that is too much closeness for you, there are other rooms and accommodation styles at the resort. http://ambergriscaye.com/victoriahouse/index.html
For some reason the website doesn't seem to show the 'private guest house' that I am talking about, so you would need to ask about it.
Some more of the advantages to this place (VH private guest house), is that it comes with its own separate (and decent sized) pool and is at the far end of the resort grounds, however, you have easy access to this beautiful resort as a whole.
I found this to be the most distinct and attractive property that I have seen on AC. Granted I have not seen them all, but I most certainly have seen and/or toured through most of them.
Victoria House is accessible to San Pedro Town, as it is on the southside. You can golfcart it, or taxi into town with no problem at all, all hours.
The grounds are beautiful.
The only caution that I would throw your way, is make sure that the extremely upscale home that is being built next to the Victoria House 'house', is finished (there was also another unit house being built behind the 'house' on the Victoria grounds). You'd want to be assured that the construction is complete so as not to be disturbed by any building noise. (both of these places looked near completion when I was there end of Feb.)
Another option is Banyan Bay, very nice resort with two bedroom units, also on the south side. http://ambergriscaye.com/pages/lodge/banyan.html
And the Belize Yacht Club is a third option. It has some lovely suites and is much closer to town, walkable actually. I've done the walk many times, most often in the day, but it can be done in the evening too, in a pinch. http://www.belizeyachtclub.com/
By the way, in case you are wondering, I'm not a travel agent, just a lover of AC and environs.