Check out the official tourist board site:>http://www.visitpembrokeshire.com
Firstly, I would like to mention a place where you might like to stop on the way to Pembrokeshire = National Botanic Garden of Wales - which is just east of Carmarthen. https://botanicgarden.wales
Basically, the whole of Pembrokeshire is scenic / nice countryside except for a few oil terminals in Milford Haven.
On the south coast, be sure to visit Tenby and I would also try and take the boat for a visit to Caldy Island - which I think is closed on weekends. Going west from Tenby, check out Shrinkle Haven before moving onto Manorbier.
Find the village of Bosherston - park car by church and take boardwalk along the lily pools to the coast - then walk east to Barafundle Bay (which can also be reached with a shorter walk from Stockpile Quay). On returning to car at Bosherston - continue down back road to St.Govans Chapel - which is wedged in the cliffs. From here, a 10 minute walk west will bring you to the cleft known as Huntsman’s Leap. (The military range may prevent you from entering this area but it is always open on weekends on in August).
Return to Bosherston & take B4319 westward. After a short distance, you will see 2 old tanks outside an army base. Take next left - if military range area is open - and follow the small road to the car park by the Stack Rocks. Now walk 5 minutes west to see the Green Bridge of Wales = a huge sea arch. Here is the phone number for there military camp at Castlemartin = 01646 662499 or 01646 662285.
Pembroke has a very large Castle. http://pembroke-castle.co.uk
On the west coast, I would head to Marloes and if you want to see seabirds, take the ferry to Skomer. However, top priority would be to go to St.David’s and have a stop at Solva on the way. The coast between St.David’s and Fishguard is much steeper than the south coast. Stumble Head is worth a visit but the roads are narrow. (You may have to drive backwards to a passing place).
Inland, you have the Presell Mountains - from which some of the stones for Stonehenge were taken. Find Newport (Pembrokeshire) - which is an attractive little place. Nearby, down some back roads is Pentre Ifan Burial Chamber - well worth a visit in my opinion if in this area.
Go further north again and you reach Cardigan. A short distance up the Teffi Valley, you reach Cenarth - where you sometimes see men on the river in Coracles. However, about 4 miles NW of Cardigan is the lovely little bay of Mwnt - but be prepared for some narrow roads. You may also like Llangranog, Aberaeron and New Quay - which are a bit further up the Ceredigion coast.
If you go as far north as Ceredigion:>http://www.discoverceredigion.co.uk/english/Pages/default.aspx