In Sanfermin there seems to be even more, especially around the old part of town, where there seems to be a bar available at every twenty steps. A few of them are quite large and spacious, but in general the typical city bar is small and crowded ( In Sanfermin they seem even smaller thanks to the crowds). One reason why there seems so many is the fact that some establishements that serve as butcher's, baker's or whatever, throughout the rest of the year, turn themselves into bars for the duration of the fiestas. You would be surprised. The bars of the Peña Gangs only are open in july by Sanfermin, you can try to go there, it´s amazing.
In general, the bars are well-manned by barmen or barmaids, but there are times when a little patience is requiered when it comes to ordering your round. And during the fiestas don't get upset if someone steps on you, douses you with drink, bumps into you or when the barman serves you up the drink in a cheap plastic glass. That is all par for the course in the old part of town. Should you wish for something more neat and chic, then you'd better head out to some of the suburban districts like San Juan or Iturrama.