I would like to repeat the experience of last year in London with https://www.mediawiki.org/wiki/VisualEditor/Translathon .
I don't know if I'll create tasks for all the following things, but the first steps which come to mind are:
set up "rally" page, with Siebrand's assistance, including stats;
announce precise time and date where people in Mexico City can gather and meet me and hopefully some translatewiki people during the hackathon; remote people can work wherever they are! Don't forget to tell VE translators about it.
Current translation statistics:
Main page at https://translatewiki.net/wiki/Project:VisualEditor/2015_Translathon ; session is on Thur 16 at 4pm.