They're speaking their plans, and there's plenty others dealing with the sprites to give them the time to speak. Tidus isn't immediately about to draw attention to them either, and with the talk of spells-

"Here, take this too!"

Tidus takes his attention off from the cage to reboost their barriers, extra fortification on top of what Romeo had to offer. If winds were thrown their way, perhaps a Shell--surrounding each of them briefly, one after another--would be able to deflect some of it.