Jones as with Williams, Edwards etc are reasonabl;y recent English imports into Wales. The convention was, and some are reverting to it, to be referred to as someone's son or daughter as Siôn ap Rhŷs (John Rhŷs' son) which transformed itself into Siôn 'p Rhŷs then Siôn Prhŷs and so until John Price and similarly Pritchard is ap Rhisiart, Probbert is ap Robert etc (Jenkins is ap Siencyn by the way)
A problem with asking how a particular word is pronounced in Welsh is that there are as many Welshes as there are places. Words are not only pronounced differently but there may well be totally different words. for example up here in Betws-y-Coed 'now' is rwan whereas Siân would probably say nawr and when she goes into B & Q for an eighth of a gallon of emulsion I suspect it would sound very much the same in English and Welsh "pint o' paint" where as I would ask for "paint o beint" which would sound more like paint o' pint" though we would both spell it the same (wouldn't we?)