well i dont think its all that dangerous honestly (ive feared for my life much more here in the states) but then again im not a white female that looks like she has money and i spoke the language. however i did meet a few Spaniards who hitched all around Mexico and a Bulgarian guy. actually i met more foreign travelers in mexico then i ever did in the states and none of them where american.
the places i went to in order was Mexico city, Morelia, Colima, Guadalajara, Leon, Guanajuato, Oaxaca, Chiapas, Salina Cruze, Campeche, Merida, tulum, playa de carmen and cancun.
the places i would recommend are : mexico city its a massive place you can find anything you want especially in Tepito but be careful there. check out "el chopo" its a saturday punk flea market they also have shows, aint nothing like it in the world. oaxaca city is awesome too. drink the mescal there oooh and the chocolate and 100 pesos gets you a big ol bag of weed. guanajuato is cool especially if you go for the cervantino festival its a month long in october. its built in the mountains and also has underground tunnels that you can sleep in if your a bum. san cristobal de las casas chiapas is prolly my favorite place in the world. cheap cheap cheap booze ask around for "posh" also known as "whiskey maya" and at the market near downtown 10 peso packs of cigarettes thats less then a dollar and a carton is 60 pesos all of chiapas is pretty cheap. its filled with cool people there is also no narco cartel shit going down there. you'll hear a lot of the locals speaking indigenous languages and there you can find the caracolas where the zapatistas live. its an awesome place and highly recommended