Which are do you live? I know several good spots on Hong Kong island, less so that don't require a bit of a journey if you're right downtown in Kowloon. HK island though is great, it has lots of pretty easy spots to go have a look around and there's one small toad that is more common on the island than out here in the New Territories, I haven't found it yet, but I will... :O)
School doesn't need to be a big problem, you don't need to be out late, most frogs seem to start calling right after sunset, so right now that's about 7pm and several species are calling before then when it's overcast. We often stay out until close to 11, but that's just because I drag it out, we could easily pop out for an hour or so and be home by 9pm. Plus there's always weekends.
To anyone else still reading this I would like to point out that I am a good and sane person, I can even pass for normal in public places such as bars and restaurants. I just get a real kick out of wildlife, so am happy to spend some nights a week being bitten by bugs, getting sweaty in marshes, falling over in streams and looking ridiculous and suspicious wearing a head torch out in the bushes at night....
Anyway, here's what we've seen so far in just 3 months of looking:
Amphibians Asian common toad, paddy frog, Hong Kong cascade frog, lesser spiny frog, green cascade frog, Gnther's frog, marbled pigmy frog, brown tree frog, Chinese bullfrog, brown wood frog, Asiatic painted frog, Butler's pigmy frog, Hong Kong newt, giant spiny frog.
red-eared slider, Reeves' terrapin.
Chinese gecko, tree gecko, four-clawed gecko, Bowring's gecko, tokay gecko, Garnot's gecko, changeable lizard, Reeves's smooth skink, long-tailed skink, brown forest skink, slender forest skink, Chinese skink, Chinese waterside skink.
red-necked keelback, Chinese cobra, Burmese python, common blind snake, king cobra, many-banded krait, Anderson's stream snake, greater green snake.
Plus a few mammals.