You may notice a few differences, but the main patterns are pretty similar across Wales. You will also meet a number of different patterns if you read and listen to the media.
This course does not teach any particular dialect. It is based on a middle of the road Welsh which forms the core of Welsh for Adults courses, so if you live in a particular part of Wales you may also be learning various local dialect patterns and words there.
For example, the standard dw i ddim yn... may be dw i'm yn... in informal usage in some parts of NW and NE Wales, but sa i'n.., sana i'n.. or smo i'n... in various mid, SE and SW Wales dialects. So as to maintain a general coverage of the language in a manageable way, this course does not cover any of those dialect variations.
As you learn more, you also notice variations across different parts of north Wales.