Not GP but I live in Philly, a very dense walkable city. It is absolutely reasonable to set a speed limit below 35 mph on most of our streets. Especially in residential neighborhoods, but honestly ideally pretty much everywhere in Center City and a good distance away from there too.

EDIT: And in fact most of the residential streets here are 25 mph, and I think only that high because it's the minimum posted speed limit in the state of Pennsylvania. (I'd like to see that lowered personally, and more importantly some traffic calming that's actually effective.)