Yes, you can walk down a very steep track which comes out behind Jacks bar, or I think there is a small track off the road behind the beach, although I've never done it personally I've seen plenty of locals arrive that way. It's a fair walk to town and quite hilly but doable if you're fit and used to the heat. The other alternative is get a taxi or water taxi which are both very reasonable. Be aware that petty crime in Bequia especially around Princess Margaret beach is prolific at this time of year, so make sure you lock your house up when not in it and don't leave things unattended on the beach.