The first census that I'm aware of was 1749, widely available and published by Garmendia Leal. The second one I've seen was 1753 but it was much more limited in info compared to the 1749 version. I know there was an 1841 census because I've reviewed a paper copy and I think there was an 1824 version also but I'm not sure about the last one. Check the inventory of the UTPA historical collection.
Regards,
D. Cano