Is certification really necessary to teach in PL?
It's not stictly speaking necessary, but you won't get paid as much without a Celta and you won't be hired by the school with the better reputations.
If you want to work in a Callen method school then you'll be fine, but you'll end up going nuts parrotting sentences to kids with no real interesting in learning.
I must point out though that the teaching English train sailed a long long time ago.
MOney is crap and conditions are usual sh!te too. You won't be paid during holidays (including Christmas, Easter and all the other nonsense public holidays Poland has).
Bielsko doesn't have many foreigners living there so you should be fine with finding work.
Only advice I can give is to learn some Polish, living here without knowledge of the language is doable, but it ain't easy.
Don't forget you'll have to register as self-emplyed and pay your own tax and health/social insurance.
Tbh, I wouldn't advise moving here as a teaching, go to South Korea, that's where the money is. You'll survive here on a teacher's wage, but you won't save much and don't forget about the long, brutal winters.