You might be better buying them at duty free on the way in (but watch the allowances because they do check - loads of people on our flight had to pay extra tax due to taking more than they should in)

We only ever saw American brand Bensons and Hedges when we were there. No L and B at all,although they are available from duty free on the way back home.

There is a duty free you can use at arrivals at Cancun but we didn't go in, so don't know if they sold L and B or not.