LFS can refer to pet stores that carry fish, but should only be applied to fish only stores so that local fish store or LFS becomes a more clearly described type of store.
IMO, any store that carries more than fish is a pet store. pet stores do not make money, or depend on fish sales or products or happy fish customers to run. buying fish or supplies from pet stores may mean you are getting something other than a quality product. this isnt written in stone, but can be a good indicator of the quality of care, knowledge, and sales representatives. there are always exceptions on both ends.
just make sure when you use LFS that you describe it as fish-only or pet oriented. JMHO.