Saturday - 10/20 - Halloween in the Hammock at Gumbo Limbo Nature Center, 1801 N. Ocean Blvd., Boca Raton. Join an hour-long nighttime nature walk with ghostly guides and ghouls. Walks departing every half hour from 6:30-9 pm. Ages 6 to adult. 6:30-10 pm. Advance: $7/members, $10 /non-members. Walk-ins: $15/person. Reservations: 544-8615.