Result: I finished in 30'56", a good 4 1/2 minutes shorter than my previous time for this course. A definite improvement.
Of course, the implication is that if I can finish my weekday run in less than 30 minutes, I need to extend it. The logical next step would be running home instead of taking the cable car. I was forced to do this once during a heavy rain when the car went out of service; after the initial near-vertical hill climb, it wasn't too bad. But I've only done a round-trip on this particular run once since. Given the cable cars' slow speed and infrequency of service that time of day, however, I shouldn't have to get up too much earlier to accomplish the out-and-back.
I may also change my ratio of walking breaks on my long runs from 5/1 to 9/1, the latter being what I used more successfully in previous training. This strategy may backfire as I only have two long runs left before the half-marathon race (the others being six miles or less), but we'll see.