Haven't been on Liberty, but I do hear great things about Guy's burgers, don't think you can go wrong there. As for a beach walking distance from the ferry in St. Johns, don't think they are that close. They do, however have cabs that can take to you the beach you want. It is an absolute beautiful island, you may enjoy the cab ride. Have been to Trunk Bay there a few times and love that one. There are a few other good ones there.. Do you plan to snorkel while over there?