LA I don't really know. But SF and NYC (especially) are relatively challenging to drive in as well. I do agree that, especially pre-GPS, Boston/Cambridge/Somerville are most challenging by the almost complete lack of any sort of a grid and all the weird intersections. When I moved back to the area with a car after grad school--though not to the city itself--I think it really took me at least a couple of years before I felt comfortable navigating more or less by instinct rather than having to constantly refer to a map.