I was able to dig up some more precise information on the strength of the Spanish in east Florida.
The Third Infantry Battalion of Cuba, stationed in St Augustine, consisted of 4 companies of Grenadiers (about 40 men each, plus officers) and one company of artillery for the Castillo and associated redoubts.
There were four companies of militia in St Augustine; one for the Spanish residents, one for the Mahones(Minorcans), one for miscellaneous White residents, and one for Free Blacks. Amounting to about 240 militiamen.
North of the city were another 180 men mustered in 2 companies of militia, mostly in Fernandina. When tensions were growing and Georgian raiders seemed likely in 1811-12, the governor raised a supplemental squad of 26 dragoons on the northside of the St Johns River.
So, uh, scratch any real resistance from San Nicholas. There was also an old abandoned battery, San Vicente de Ferrer, somewhere on the bluff between Newcastle Creek and the Charter Point neighborhood, that the Patriot rebels reoccupied.
I also forgot that there was a
Fort Picolata at a ferry crossing on the middle St Johns River, 21 miles west of San Augustine. The Fort controlled access up the river and communications with the Seminoles further west. It also seems to have been as understaffed as San Nicholas, and likewise occupied by Patriot forces.
So in all, the Spanish really put all their hope in holding Augustine with the promise of aid from the Indians and eventual reinforcements from Cuba.