Considering the fact that Mexicans seeking a better life aren't the only people crossing that border, the Guard darn well better be armed.
Of course. If not they'd soon be a laughing stock at best, if not helpless targets. But it wouldn't be the first time. I remember hearing that some of the Guards on duty after 9/11 weren't issued ammo. It came out months later. There's been some pretty PC/stupid engagement rules in the past, where troops have been "shown" but not able to act normally. Think SS Cole, for example.