I was very surprised to see how diverse and mixed Mexico city was. My visit was short (just 9 days, with many day trips from Mexico city in between) so I only got a teaser of the whole deal. Still, since my couchsurfing hosts were scattered around the city, I was compelled to take the public transit and explore neighbourhoods; and I was glad to do that.
The historic downtown with one of the largest city-squares in the world gave me and idea of how it would have felt in the colonial era back when the Spanish were ruling (you have to ignore the crowd and noisy cars). The Coyoacan delegacion, not far from crowded downtown, felt like a village that escaped the mad growth that rest of Mexico city saw. Then there was the green Chapultepec park and business district, rich Polanco (Miguel Hidalgo), residential Benito Juarez, the huge Tlalpan to the south and canal maze at the Xochimilco borough.
When I go next time, I will try Mexico city's free bicycles to go around during the day. It's possible to rent these bicycles for the day for free, somewhat similar to Toronto's Bixi program. In fact, some streets are closed for vehicular traffic on Sundays in order to promote cycling.
It was strange but newspaper stands carry lot of material that I thought was semi pornographic in nature. People seem to enjoy reading magazines with pictures of naked ladies (and sometimes men) on their covers. Quite odd in a conservative catholic country, especially seeing teenagers huddled around a magazine in a crowded subway. I bought few magazines to keep as souvenirs, but I lost them somewhere…
One convenient thing in Mexico city is the plethora of public telephones. Several of these use phone cards, but there are lots that just accept coins. Random observation: Public phone booths in richer neighbourhoods cost 1 peso more.