Yes, thats the entire point of the Public folder. Anything in there that you give the explicit link for is available to all to see. There is also an option to "share" from other folders, however, these require you to name people and for said people to authentication to be able to see the contents of the folder. Not sure how it works, but I assume it is for sharing between other Drop box users(ie, thats the user you select to "share" with).