Moisés,

It's a good catch, but the period ranges only up to June 1811. Nonetheless, most of John Grant's letters are written from Azeuche, supposedly where he was captured (according to Pereira).
Either it is his main base of operations, or, if we go into 'spy vs. spy' universe, a codename.
Anyway, I'll be in Google Earth trying to find this town.

Thanks,

Jorge