Even as a find this post a bit suspicious from a first time poster...

The security is at the Moon Palace for a world conference on AH1N1 being held where the President of Mexico is expected to be in attendance.

The Por Esto article and Youtube references are allegedly from a citizens vigilante group that executed

3 members of a notorious drug cartel involved in citizen shake downs, drug trafficking & illegal immigration of Cubans.

If you're going to Cancun and staying in the tourist areas, you should have relatively few safety concerns, certainly, no more than any other major worldwide tourist destination.