My Motorola box from Comcast has the same thing - pick an output. However, in the cable box menu (setup/audio/audio output if you have this model) I can change the digital audio output to PCM instead of Advanced (DD or other surr format) anytime. This would preclude the need for additional or changing connections.

I'm assuming you are using TimeWarner's boxes down there? I can't imagine there not being a setting like this on all digital boxes, since there are lots of folks with only an HDTV connected to that optical output. Oh, wait, it's a cable company, so yes I can.