I've spent a lot of time in that area but all it on boats. St. Vincent is OK but a wee bit funky. The areas around the volcano are real cool but take a guide with you. You definitely don't want to wander into somebody's secret agricultural area.
A better choice might be one island south about 10 miles called Bequia. The people are much friendlier and you can take some day trips to some really cool islands south of that.