How long are you vacationing that you need more than 10 packs? If 10 packs won't last you 2 weeks you have bigger problems than customs.
It doesn't matter if you brought them from home or purchased them in the duty free before you arrive at Mexican customs - if you exceed what they now allow(200 cigs / 10 pkgs) you are going to to be hit with a duty penalty on the amount that exceeds what is allowed. Welcome to Mexico best advice -just do a quick Walmart(etc) stop for cigs once you have your transportation.
