Take the 1 or 9 train to the Franklin Street stop. Emerge at the corner of Franklin and Varick Street. Walk south on Varick Street as it becomes West Broadway. You'll pass Worth Street, once the center of 19th-century New York's garment trade. At Duane Street, make a right and walk west to Hudson Street.
Here you'll find the small, shady Duane Park, a great spot for sitting outside and people-watching.