In order to handle arrays with the $resource service, it's suggested that you use the query method. As you can see below, the query method is built to handle arrays.
{ 'get': {method:'GET'},
'save': {method:'POST'},
'query': {method:'GET', isArray:true},
'remove': {method:'DELETE'},
'delete': {method:'DELETE'}
};
User $resource("apiUrl").query();