Your young bloke will have a blast, Spain is a beautiful country with beautiful women, and a very relaxed attitude to life.
But Zauratz is not exactly the best place in Spain to go surf, it has been used as a back up location when the swell has been too small for Mundaka, but it is a pretty average beach break. Obviously he has to go to Mundaka, just to see the town, and if he is lucky he might even catch some late season swell. If he can sneak one from the local rippers, then he will have 200 meters of freight train barrel running down the bank.
Ted is right, San Sebastian is a killer place, with pretty good waves and an awesome nightlife.
Another place he may want to look at is Rodiles, another river mouth further west, similar set up to Mundaka, but less crowds, and he can camp on the grass just in front of the beach.
Public transport in that part of Spain is not great and for surfing a car is pretty much a necessity.
One thing to remember is that in summer, every European heads to one of the coastlines, either the Med or the Atlantic and accommodation can be really tricky to find, even camping, although if he is going now it should be not so bad, come late July or August it seems like every place is full, I spent two days driving just to find a hotel a few years ago.
Like anywhere, tell him to respect the locals, the Basque people are so friendly but they are also a proud race and don't take **** from foreigners. There is quite a few French and Brit surfers who have found out the hard way.
That Coastline is not so exposed to swell in summer, the storms are more to the west, unlike winter when they push down from the north, so if it gets smaller, he can either head up the coast to Hossegor, which picks up a lot of swell, and is a great place, or across to Portugal.
Sourcing boards should be no trouble, you can pick up a local shape for around 350 euro brand new, or a second hand one easily from other travellers.
Hope he enjoys it, I am off there myself in about 2 weeks.