There is a good days (slightly boggy in places)riding in the Preseli hills about 10 miles N of Bluestone but that’s about it for Pembrokeshire. Brechfa trail centre is just the other side of Carmarthen.
I can’t show you round because I moved somewhere where the biking is better.
If you do ride the Preselis I’d recommend a pint outside the Dyffryn Arms, Cwm Gwaun, on a sunny afternoon.