The balcony issue is always one of the most stressing things about arriving to Pamplona.
When to rent a balcony to watch the running of the bulls, is always one of those things that you are not sure when to do so. Well today is May 7th. Guess what, you are a bit late.
Sorry to rush you, but you should have started in February with this. Don´t panic, you are still on time to do it. I always recommend to book your hotel (hostel, Airbnb…) the first thing, and once you have the dates go for the balcony. Right after Christmas, you should do the hotel, and by February the balcony.
Now in May, you will still find good balconies. But you should not take too much time to do so.