St Davids is a great little base.
Caerfai Campsite (http://www.ukcampsite.co.uk/sites/reviews.asp?revid=5274) is the best in the area IMHO.
Food
1. Farmers Arms in St Davids os good for classic pub food, best enjoyed on the terrace at the back.
2. CWtch in St Davids is very good
3. The Bench is very average – service is shite IMHO. Good Ice cream though.
4. Pharmacy in Solva is good.
5. Refectory at the Cathedral is pretty good and a nice quirky dining room.
6. The Sloop at Porthgain is Good, but The Shed is very good – excellent seafood.
The best breakfast and coffee is at Jones.
The Pebbles Cafe is poor, but the gift shop is OK for higher end tatt.
ToDo
Tourist Information in St David's should be your first stop
Walk the coast path
Beaches – Caerfai is my favourite
Cathedral – worth an hour of anyone's time
Walk from Abereiddy to Porthgain – Sloop and back again is a nice way to spend an afternoon.
If you are feeling energetic, coastearing is the local adrenaline sport of choice (TYF do guided trips)
HTH