Yeah, if they found more, it was off-screen. Not to say they couldn't have grabbed ammo off of any of the giant group of dead soldiers around the CDC, though. That should have set them up for life, as every one of them would have had machine/hand guns and ammo on them, although they might have to add some together to combine clips and whatnot.
Also could have found stuff in the traffic jam easily enough, they had forever to look...
Also could have found stuff in the traffic jam easily enough, they had forever to look...