Melbourne might be a bit far.
Check out:
All Restaurant General Manager Jobs in Port St. Lucie, FL | Indeed.com
Also, if you live in Port St. Lucie, be sure to expand your search into Stuart/Jensen Beach and Fort Pierce. PSL, for all its population and growth, is still very much "behind" in developing restaurants. A large cluster of restaurants is in the St. Lucie West area, Tradition, and US-1, but beyond that it could probably do much better, especially in the "chain" restaurant department.
You can also start sending your resume out to restaurants that are looking for managers in the Treasure Coast area:
http://treasure.craigslist.org/search/fbh?query=manager
At this time it doesn't look like much is available, however.