Hi Diane... I don't think you'll find too many recommendations for taxi companies in Pamplona. Unless there is some sort of dedicated chauffeur service you'll just be relying on ordinary taxis. These will be licensed so should be alright.

Pamplona is FULL of foreigners most of the time so it won't be a problem finding English speakers. The entire population of Australia and New Zealand was there in VW Campers the time we went!

As long as your student doesn't wander down the streets in white trousers, white shirt and with a red scarf at bull running time, they'll be fine.