As some coup-watchers have been pointing out on Twitter, the first place to look is to see what foreign diplomats are saying. As of now, no foreign embassies in Zimbabwe have issued any advisories noting unusual troop movements in Harare and the travel bulletins just now released by the British foreign office did not have any notice of political developments in Zimbabwe.
It could just be the military moving tanks around to show Mugabe that they're serious about their threat.
I would like to point out that most foreign citizens wouldn't willingly go to Zimbabwe. If they went to an African country it probably would be Egypt or South Africa.
