It's about 18 days from egg laying to hatching, then 20 - 40 days for the fledglings to leave the nest, so in about two months we'll probably be hearing the frequent loud squawks of the fledglings around town, bugging their parents to beak feed them even though the food is right there on the ground ready to eat.
I started out getting their attention by making noises. Once I knew they were aware of me, I tossed the food into a flat area where they could easily collect it all. Once they realize you're good for food, it won't take much effort to get their attention. They start looking for you and will fly up when you come outside. I've had them swoop very close to me to get my attention if I hadn't noticed them yet when I'm outside. They'll also caw to let each other know that you're there, so more will fly up. Sometimes there's one that will stay in a tree overhead as a watch if there are cats or other possible dangers in the area.