Is there any pink in their comb? Do they have pink wattles coming in? Those would probably be the first possible signs at this age, but it might be a little early to say for sure.
I looked on the Ameraucana site for a list of breeders by state. LUCKILY there is a breeder of Bantams only 45 minutes north of me. I bought a hen (Grown and laying -- $10), he gave me another hen with crooked toes (also laying), and I bought the only 2 chicks he'd had hatch out in 24 hours that weren't spoken for ($4 each). He thought he had 3 but turned out he counted wrong and only had these 2. Got my fingers crossed for more females!
There is NO pink yet in the comb and whatever sex they are, they must be the same because their feathering and tail growth has been exactly the same for the month I've had them.
Cuties! It's too early to say with certainty that they are pullets but they aren't showing any cockerel signs yet. I'd wait a few more weeks to watch for comb changes. If they still have little birth pale combs at 8 weeks, odds are excellent for pullets.