Just coming back to close this thread. Thought the clockspring was the problem, based on multiple indications - cruise control won't engage, airbag light comes on, and horn won't work. Searched and couldn't find a replacement for <$180, so decided to start with some troubleshooting and hope for a cheap fix.
Took the steering wheel off tonight and actually disassembled the clockspring housing. Had read somewhere on here or another forum about someone doing that. Tested continuity from both ends of each trace in the ribbon cable, no short or open circuits. Then tested the continuity of the horn button on the steering wheel (actually on the airbag module) while it was off. No problem there. Tested voltage on the pin for the horn in the connector which plugs into the clockspring, got good reading (12.6V). Jumpered from that pin to a body ground and heard the relay click. At this point realized that I should have taken JP's advice and tested the horns... BOTH low and high notes are blown. I felt really stupid...
Not sure how that happened, but we'll be going to find new ones if I can't dissect these and fix them... I haven't priced them, but I'm betting they're pretty inexpensive.
After reassembling everything, found that my diagnostic reasoning wasn't very sound - the cruise control light on the instrument cluster comes on when the on/off button is pushed, which immediately eliminates the clockspring. Also, when the airbag light is on, the air conditioning blower won't run... jiggling the ignition key will sometimes remedy the problem. That can't be the clockspring causing that. There must be something going on in the ignition module, but I haven't a clue how that would work. I'd love it if someone could explain it.