I happen to live in a neighborhood of Brooklyn with both extensive Kosher and Halal options (which is probably not a coincidence, since there is significant overlap in rules). But Mexico City has a different cultural mix than New York City or London.
I can understand, though, that it may be too expensive and difficult to get Kosher or Halal meat, or indeed fully catered meals, for Wikimania in Mexico City.
Bur I would suggest going to a supermarket and getting something like a pre-packaged hummus with K and H marks, and some plain fruits and vegetables, so folks like this can at least have snack options during the conference sessions, and that can tide them over if they want to go out for a full meal fulfilling their dietary preferences later.
Thanks,
Richard
(User:Pharos)