Being able to buy in person is great compared to having something shipped from an unknown seller for sure. I contacted the seller of my new boas through CL and his name was in his email. I went to the BOI and found some good guy threads on him and decided to make the trip.
The majority of time a CL seller is not a breeder though so it can be tough. What was meant by checking them out is when you go to their place take a look at how their animals look and are setup.