restore message . . . cascade

I am backing up my databases with pgdump -c command to prevent duplicate
records during a restore.

When I restore the database with this command:
psql -U postgres infoserv < /tmp/infoserv-03-25-2008_12-10
I get the message to use cascade to drop dependent objects.

DROP TABLE
ERROR: cannot drop schema public because other objects depend on it
HINT: Use DROP ... CASCADE to drop the dependent objects too.
ERROR: schema "public" already exists
ALTER SCHEMA

1.) If the schema is not dropped during the restore, is stuff in the
schema being duplicated?
2.) What flag can I add to the pgdump command to initiate the cascade?
3.) Is it best practice to drop the schema and dependant objects?

Thanks,

Marc