Try browser.wait()
https://code.google.com/p/selenium/source/browse/javascript/webdriver/webdriver.js#519
browser.wait(function(){
// Wait until condition is true.
return element(by.model('myValue')).evaluate('myValue')
.then(function(v) {
// I'm not sure if it will evaluate to a string, try it.
return v === 'true';
});
}, 10000)
Where 10000 is the timeout in ms.