The appearance of the JONES surname in Wales before 1600 is finally completed with Cardigan and Pembroke counties. All counties in Wales have the occurrence of an individual with the surname JONES except Anglesey. [Isle of Mon.]
For Cardigan is Thomas Jones [99/40] 1558-1579.
For Pembroke is Owen Jones [242/66] 1558-1603.
It would seem that the JONES surnames moves essentially east to west, with Pembroke being the last county to have an individual JONES get involved in the English legal system. Anglesey held out! It would be interesting to investigate this further. At least if you had an ancestor from Wales before 1600 [with the surname JONES] you might be able to begin your genealogical investigation. Anglesey would be least likely to have a JONES family.