It is really not relevant to YOU if someone else experienced effects of altitude sickness. For DF the issue is not just the altitude but also the air quality which on some days can be excellent and on others not so much. I visit family in DF and Toluca (even higher at 2,800m) regularly and sometimes I feel it even as most times I do not (until I try to run upstairs to get my phone before leaving the house!). If you have been to high-altitude locations (2,000m) in Europe or elsewhere without any ill effects then you will most likely be just fine in DF. But if you do tend to feel the effects of altitude then taking acetazolamide (trade name Diamox) at least 24 hours before going there may help.