I'm English and moved to North Wales after being offered a job there. It's one of the few roles that I can have here, because I am not a Welsh speaker.
I am, however, learning! There are online classes (Dysgu Cymraeg or Popeth Cymraeg) and in-person ones. Sometimes people speak Welsh to me, but are very accommodating when I say, "Dw i'n dysgu Cymraeg!" (I am learning Welsh). They either switch to English, or speak Welsh slowly and clearly to me! Do make an effort to learn Welsh, and if your house has a Welsh name, please check the pronunciation and meaning with the estate agents or your neighbours! (I have met a few people who have no idea how to say where they live...). Oh, and being a member of a choir is much more popular here than in England!
If you live in Flintshire, it seems predominantly English-speaking. Denbighshire (at least around Corwen) is more of a mixture of both English and Welsh (but mainly Welsh if you're rural). There are a lot of Welsh-medium schools around here, but there are a few English ones, too, even though they have Ysgol in their names. Quite a lot of the local primary schools are tiny. 45 minutes to school seems a long time, but a lot of students live rurally and are bussed in to the local schools (including primary schools) and colleges around here. Friends who had Welsh-medium educations and English-speaking parents just learnt everything (e.g. maths) in both languages out of necessity for help with homework!
Erm... you might feel like a shoplifter when picking up prescriptions, as unlike in England, they are free in Wales. Depending on where you live, you might find country roads a bit different to get used to, or driving behind farm vehicles, or in the dark because there aren't always street lights. It's a beautiful country.