Sturbridge sits at one of the most useful highway junctions in New England: I-90 (the Massachusetts Turnpike) and I-84 meet here. From Boston, take I-90 West to Exit 9 (Sturbridge) — about 60 miles, roughly an hour in normal traffic. From New York City, take I-95 North to I-84 West, then follow I-84 to the I-90 junction — roughly 170 miles, about three hours without heavy traffic. From Hartford, it's 40 miles up I-84 East, about 45 minutes.
There is no practical public transport to Sturbridge. The Peter Pan bus line runs between Boston South Station and Springfield with stops at Worcester, but it does not stop in Sturbridge itself. Unless you can arrange a pickup, a car is required.