The taxi in Sanfermin could be a sound idea thanks to its versatility at a time when the traffic flow gets rather complicated throughout the fiestas week. It should be borne in mind that many streets in the downtown and old quarter are closed to traffic during fiestas and other streets may be temporarily cut off along the day due to fiestas events such as the running of the bulls, the kiddies firebull or even the nightly setting off of fireworks, not to mention the daily parade of the Giants and their Entourage - the Comparsa de Gigantes y Cabezudos. Taxi drivers, thanks to their professionalism, will know the quickest routes and short cuts to take in these cases and, in addition, they are sometimes allowed access to some streets which are closed to normal traffic.
To hire a taxi it is necessary to make a phone call (Teletaxi Sanfermin 948 23 23 00 / 948 35 13 35 or Ecotaxi +34 609 45 21 91), although sometimes if the green light to indicate that the taxi is free is lit you can hail down the taxi with your hand from the street sidewalk. There are also some taxi sites located around the city (Check a local city map or consult the web page of the body responsible for taxi management) - the Mancomunidad de la Comarca de Pamplona. There are different kinds of taxis in use; in large size or for cases of disabled people, etc.
If your place of stay during Sanfermin is located outside the city of Pamplona, this is a list of taxi services available issued by the Navarra Government which may be of help.