I spent several days in Mexico City In January of 2003 in order to break up a return flight from Cuba. I had been there for a few days in the summer of 1985 and was intrigued with it enough to want to return.
On my first trip I had stayed in an area known as the Zona Rosa. This time I found a good cheap hotel near the Zocalo, the main square of the city.
Mexico City is of course an enormous town but it has a very good subway system so getting from place to place is easy not to mention cheap. Actually Mexico City is inexpensive overall and offers great value to the traveler.