Mexico is -6 hrs GMT so its -7hrs (or is it -5hrs?) BST providing of course there isn't a Mexico Summer Time. That would put the kickoff at EST at either 8:15pm, 9:15pm or 10:15pm.
Providing there is a Mexico Summer Time as Mexico is in the same zone as Central time (US) then the kickoff should be at 9:15pm EST
If there isn't a Mexico Summer Time then the kickoff will be either 8:15pm EST or 10:15pm EST. This of course all depends on whether the official site has the right time.
It's quite straighforward.