We took the Basque tour last fall, you will love it. Since learning about the Running (both of our guides had done it) I think it would be wonderful to experience. I understand your crowd concern. But with a tour, they plan all the logistics. We asked so many questions of our guides how the city handles all of it, quite fascinating! I wouldn't attend it alone, but am sure they have it planned out perfectly. You may be seeing it from a balcony. You could call Ricks Steves office for further info in how they handle it.