I know that RIR's can be sexed with the wing tip method. That's how I sold off all my extra RIR roos (3) from my straight run assortment and ended up with 1 roo and 5 hens.
There are only a handful that can't be sexed by their wings. Silkies are one of them, so if I get any silkies, they will be colors that I won't mind having a rooster in.
Luckily, we live on five acres and our neighbors love fresh eggs once per week. lol. My chickens are also much better behaved than one of the other neighbors bantams. When I free range, the chickens know where the property line is (either that or they don't want to get too far away from their feeders). I've had bantams from our other neighbor (1/2 mile away) show up here at feeding time. I'll make sure they eat, but not when they're on my property, then I'll hike them back home. At least his chickens are sweet.
My only mean roo (out of the 11 full grown ones) is my RIR, and he is locked up with his five RIR hens to keep him busy. All of the rest of them are too interested in trying to be picked up and fed treats!
Anyway, they said that the chicks would definatly be in between 8:30 and 9:30 - depended on how quickly they could get them out onto the sales floor. It's 8:15 now. I don't think that the cashier I was speaking to yesterday understood that, since this is a rural area, 300 chicks won't last but about an hour once people get wind of them being there.