My last trip to Mexico City my company was very concerned, I was picked up by a known driver and was told to only leave the hotel with the armed guard they had provided, which included escorts to and from the airport and our offices. Personally I found this a bit over the top and that there was a great place near by that had amazing rolled tacos and a good happy hour a 5 minute walk (shh don't tell )

Really though, I would caution don't get in a cab you haven't prearranged and you should be fine, also KNR policy is something that might be considered (its not that expensive and worth it IMO), but that's something not appropriate for a IBB.