Doubt it will affect Cancun. It developed too early and looks like it will weaken as it moves closer. In any case all current models show it staying more than 100 miles North East. I remember when we first moved to Cancun there was a close call two or three times a year, now nothing for maybe 5 years or more and no major events in more than 10 years.
Here's the update from CNN there is also an app you can use called MyRadar that is good a tracking storms and very accurate
There is no need to worry about Danny ruining your Cancun vacation. I would be more concerned with the asteroid that may impact the Earth close to Puerto Rico in mid to late September.
