This can be done using any taxi at any location on the map however I recommend using a more modern taxi and doing this in Las Venturas area as it is mainly flat and is more of a grid like layout which makes it easier and faster to travel. All 50 fares do not need to be done consecutively in a row however you do receive a decent bonus the longer the streak you keep.
After you complete this all taxis will have nitrous and hydraulics.