Hi!
I think that the american media are doing a huge thing of a very isolated problem.
Most of the drug war is happening in Ciudad Juarez , wich is very close to the US border.
The Riviera Maya and other tourist locations are not affected at all.I've been living in Mexico for 6 years, and i never had any problems, i actually feel more insecure in the US these days...Don't cancel the excursions, in my opinion, Tulum and Chichen Itza are amazing ruins, i got married in Tulum last year, did all of these with my family and friends, everybody loved those archeological sites.
Even in the case of military check points, know that the mexican military are young and very courteous people, never had a problem travelling all over mexico for years...
I hope this will help!