and our own country has given this warning...updated 1/9/2014
http://travel.state.gov/content/passports/english/alertswarnings/mexico-travel-warning.html
with that being said -- there is no travel advisory for quintana roo (home of playa del carmen and cancun)
But... even you have to admit the warning doesn't apply to the area you have deemed unsafe LOL!
As you point out here's what the State Department ACTUALLY says
"The U.S. Department of State warns U.S. citizens about the risk of traveling in Mexico due to threats to safety and security posed by Transnational Criminal Organizations (TCOs) in the country. U.S. citizens have been the target of violent crimes, such as kidnapping, carjacking, and robbery by TCOs in various Mexican states. For information on security conditions in specific regions of Mexico, which can vary, travelers should reference the state-by-state assessments further below. "
And here is the state by state summary for the area around Cancun
"Quintana Roo: Cancun, Cozumel, Playa del Carmen, Riviera Maya and Tulum are major cities/travel destinations in Quintana Roo - No advisory is in effect. "
As I said the only way you will really be safe is barricaded in your personal bunker. Otherwise you are probably just as safe in the Cancun as you are in most of the US. (As I type this two local schools are on lockdown due to shooting in the area...)
Having traveled to Mexico, Punta Cana etc for the average tourist there's not much difference. Now when you go out to buy drugs, all bets are off. (Yes, folks I actually read a story about a guy who got in real trouble in Punta Cana. As the story came out it turned out he was out buying drugs... Hmm...Your criminal element is not made up of tourist friendly folks

)
And of course using common sense helps. Every year I read about some woman who went to one of these places, found the "love of her life" and was eventually conned into sending him all her money. Trust me, if you are a middle aged woman the 20 something is not after your good looks!