If you're really in doubt, list both. It takes about 3 seconds to type "10c to f" into Google and you have your conversion. Just make sure you mention which temperature gauge you're using - 60F is very very different to 60C. If someone elses question doesn't mention, but it's pretty obvious, then edit it in with a conversion to both F and C. Or to K as well if you really want to hammer the point home.
Really though this should go for anything where units differ between countries - for example, voltages. I received warnings once from a user who didn't realise my systems run on 240v - and why should he? I never made any mention of it in my question.
