I got in on the class at the main DMV on E. Broad as a walk-in my first try. Lucky me, right? Well, if you do sign up for a class you can still try to get in as a walk-in earlier as long as you show proof that you've payed for a later class. No need to show up early for the walk-in, they don't do the first-come-first-serve thing. It's a lottery.