What leads you to believe he was buried in Pelot? I see he is living in Fort Brooke in 1850. According to the St Augustine genealogical Society there was a Gregorio Bravo who died July 26, 1851.
If the Donato Bravo living with him in 1850 is YOUR Gregorio's brother that would make sense as Donato moved back to St. Johns county, Florida.
They are the sons of Christobal Bravo and Josefa Agueda Famanias.

You might try looking in "The Ancient City Genealogist". here is a link that will let you know what libraries have it in their holdings. You can also send for a copy of the index for $2.00.

http://www.stauggens.com/Stauggen17.html

There are also probate and court records for Donato in St. Johns County.
There might also possibly be some kind of court records for Gregorio's minor children.

Good luck.