Llan-day-lo more correct,I suspect, but general pronunciation in Carmarthen would be somewhere between that and Llan-die-lo - a halfway house! The spelling has also been Llandilo (Fawr) so perhaps some people pronounce it Llan-dee-lo. Just to confuse matters.
I'm with Gaynor here, as I am from Carmarthen.
I would say Llan-die-lo.
Llan-day-lo more correct,I suspect, but general pronunciation in Carmarthen would be somewhere between that and Llan-die-lo - a halfway house! The spelling has also been Llandilo (Fawr) so perhaps some people pronounce it Llan-dee-lo. Just to confuse matters.