Woodward Dreamcruise!!!

The middle section (roughly 12 mile road up through downtown Birmingham) is the most popular. That means the most cars, but also the most people and congestion.

If you just want to walk and see a bazillion cars parked on display, then around 13 mile is the place to start.
If you want to drive, or see more cars moving in the street, I'd recomend either going farther North or South.
Definitely get there as early as possible, as the traffic congestion gets worse in the afternoon/evening.
On the other hand, no matter where you go, or when you are there, you will see more cool cars than you can imagine.

I've got the front end torn apart in the Dart, so will be driving my '65 300 Convertible again. 8)