where are good Pembroke Welsh Corgi breeders in Maryland?

Answer 1

if you go on the akc registry website they tell the location and quality of the breeders.

Answer 2

I don't have an experience with this breeder, but I've also been looking into a corgi and they seem to be decent:

http://www.petsonsale.com/members/ezbrook/index.html

Other than that, I didn't come across Pembrokes in MD, but here is a Cardigan breeder:

http://www.heritagehillcardicorgi.com/index.html