Peggy…you have to put it all in perspective…over 50 million people visit Mexico each year.
I don't know of any mugging or robbery in Cancun…though there was something recently in Puerto Vallarta…but the story keeps changing from a "group of bandits" to a "lone bandit"…and from "the tour bus was stormed by the bandits" to the "lone bandit robbed a few as they walked along a trail"…hard to say what really happened.
Most of the warnings you'll hear about are for the border towns and usually between the cartels.
I think the reports of violence are extremely overblown…you can have crime anywhere…anytime…by anyone…never any guarantees!
And if you look at crimes in different countries…the statistics per 100,000…the US is way worse than Mexico! http://www.nationmaster.com/graph/cri_tot_cri-crime
We travel to Mexico quite often and find it to be a safe and very friendly country to travel in…I personally have traveled all over Mexico for the past 40 years and most of it by myself!
Just use your common sense anywhere you travel...and you should be fine!
But you need to do whatever is good for your own comfort zone!!
So...here's to seeing you soon in beautiful Mexico!!!