Potentially relocating to Mexico City

I am currently exploring an opportunity to work in Mexico City. If selected, I would be required to live there for 2 years. I have researched the internet, especially the Spanish news sites and have to say that I have reservations about the relocation. If you are an American currently living/working in Mexico City, I would love to hear about your experience. How safe is it really? Will I feel like I am a walking target? Are kidnappings a real concern? What neighborhoods do I want live in? Which ones do I want stay clear of? How do you travel to work. What are typical commute times? Do you cook at home or do you mostly eat out? What are the markets like? What is the quality of food like? etc. What s the shopping situation like? Is clothes affordable and attainable or am I better off waiting to go back to the states to do the majority of my shopping. Any regrets with the relocation?
What do you like most? Least? Any feedback is greatly appreciated.