Tom,
I found that the St Augustine beach does not prohibt metal detecting. St Augustine does, however you can obtain written permission:
Sec. 6-7. Excavations on public property.
No individual shall be allowed to use a probe, metal detector or any other device to search or excavate for artifacts on public property, nor can any individual remove artifacts from public property without the written permission of the city.
Sec. 6-9. Ownership of artifacts.
(a) All artifacts uncovered, recovered or discovered during the course of any testing, salvage archaeology or monitoring, as provided herein, on private property shall belong to the owner of the property upon which such artifacts are found. Likewise, artifacts uncovered, recovered or discovered during testing, salvage archaeology or monitoring on property belonging to the city shall belong to the city. However, the city shall retain possession of artifacts from private property for a period of up to two (2) years to allow for their proper analysis, cataloging, recording, and conservation, with written permission of the owner. Furthermore, the city shall attempt to obtain written permission from property owners to secure permanent ownership of the artifacts; otherwise, all retained artifacts are then to be returned to the property owner as soon as such analysis, cataloging, recording, and conservation is completed. Individuals and property owners are strongly urged to donate archaeological artifacts to the city for long-term storage, care, protection and preservation.
SO like you I thought that St Augustine was offlimits.... But I am sure that George Street area would be off limits or you would not gain permission... I will check into it further, my dad knows some folks in that area.