I'm not sure why you're having a problem unless the location entity has strings on it. I just did a quick fiddle and it works fine. Here's the HTML:
<div ng-app="myApp" ng-controller="myController">
<span>
<a ng-click="upCount = upCount + 1" href="#" ng-init="upCount=location.upVoteCount">Up: {{upCount}}</a>
<a ng-click="downCount = downCount - 1" href="#" ng-init="downCount=location.downVoteCount">Down: {{downCount}}</a>
</span>
</div>
Here's the JavaScript:
var app = angular.module("myApp", []);
app.controller("myController", function($scope) {
$scope.location = {
upVoteCount: 0,
downVoteCount: 0
};
});
It works just fine up or down voting. Run it here: