Just thought I'd update, in case it's helpful to anyone else:
I didn't give Chico the antibiotics after all... I opted to use the Goodwinol once a day and keep a close eye on the spot on his face. I started giving him flax-seed oil and garlic once a day to help boost his immune system. He never developed any other spots, and he never showed any sign of secondary infection. In fact, the spot on his face didn't seem to trouble him at all.
He had a second appointment within a week, and the hair had already appeared to be growing back. The vet even commented on the regrowth. Despite this, he (different doc, same office) prescribed
another two-week round of antibiotics.

So I kept my mouth shut (I know, stupid...), paid for the scrip (which, thankfully, was only $6), and continued to withhold the antibiotic.
It's been four weeks since his first skin scraping and diagnosis, and I stopped treating it with Goodwinol about two weeks ago. The hair is filling in the entire spot rapidly (can't tell it was bald, really, without looking pretty closely).
I'm beginning to think I should find a new vet. I don't like the idea that they wanted me to arbitrarily pump my dog with antibiotics without any sign of infection, much less
after signs of rapid improvement. I know I should've said something at the time, but what can I say? I'm intimidated, maybe.

Does anybody else have a hard time questioning their vets' motives? And do you think I need to have another skin scraping if the spot seems to be almost entirely regrown/recovered?