Hi, AJ,
I left from Irun in early May so I can't comment on August either. But I will say that even if the Camino itself isn't crowded in August, remember that you're walking through prime vacation land during the month when every Spaniard who possibly can goes on vacation. That means if there's no albergue or if one is full, you're going to have to deal with overcrowded and expensive private accommodation. We stayed in a lot of non-albergue accommodations on the Norte, more than on other Caminos, but I do know people who managed to plan their stages better and stay only (or almost only) in albergues. I just don't know what the numbers are like in August, but in May-June there was no problem. The other thing is that a lot of the "albergues" on the Norte are actually youth hostels and likely to be filled with groups of young hikers, etc. I'm sure you will find places to stay, but it might be more of a hassle than you would expect on a "lesser traveled" Camino.
Just my two cents -- Laurie