Been to Mexico City twice this year, staying by co-incidence both times at Westin Santa Fe. Lovely hotel with excellent staff but a bit disappointing breakfast. Didn't really matter though as just outside is several amazing places for both breakfast, lunch and dinner with Jin San Shabu Shabu as my favourite (but only when seated outside). It worked well both for lunch/dinners with clients and for dinners with only work as company.
Well worth the trip, through town in heavy congestion, was also the floating gardens of Xochimilco. Would recommend them anytime over the Teotihuacan pyramids. When you only have a couple of hours to see a city the experience of doing something you never done before always beats ruins no matter how old and big.
Also made sure to experience Pujol. I can understand why it managed to take a place on the World´s 50 Best Restaurants list but also why it falls as it didn't feel really ambitious. It felt, I´m no expert, as a novel take without loosing the connection to tradition on Mexican food. Some dishes was excellent, some actually quite bland. The sommelier was a joke and the discussion around which wine to choose felt like a Fawlty Towers scene. He refused to even give advise but merely wanted to know if we liked red or white and when we gave up trying to explain that it doesn't matter as long as it goes well with the food and said white he simply said that a lot of people likes Chablis. Well I don't drink Chablis. In short I was glad to have been there but will not go back.
A general rec based on the experience from these trips is also to always travel on Friday the 13th. For some reason substantially less people on the airport, in the planes etc:)