I don't think there is a sushi bar at the California Grill.
There is the bar, where you can sit. There is also some limited counter seating, where you're able to watch the chefs make the sushi, but I wouldn't personally call it a sushi bar. You probably need to have a reservation for that. If it's open they would probably let you up, but you run the risk that it isn't open.
You don't need reservations for the drinks bar or the lounge, where you can order the full menu, but they may not let you go up to the lounge if it's full.