Here is a solution that does not make a geocoding request that may return an incorrect result: http://jsfiddle.net/amirnissim/2D6HW/
It simulates a down-arrow keypress whenever the user hits return inside the autocomplete field. The ? event is triggered before the return event so it simulates the user selecting the first suggestion using the keyboard.
Here is the code (tested on Chrome and Firefox) :
<script src='https://ajax.googleapis.com/ajax/libs/jquery/1.7.2/jquery.min.js'></script>
<script src="https://maps.googleapis.com/maps/api/js?sensor=false&libraries=places"></script>
<script>
var pac_input = document.getElementById('searchTextField');
(function pacSelectFirst(input) {
// store the original event binding function
var _addEventListener = (input.addEventListener) ? input.addEventListener : input.attachEvent;
function addEventListenerWrapper(type, listener) {
// Simulate a 'down arrow' keypress on hitting 'return' when no pac suggestion is selected,
// and then trigger the original listener.
if (type == "keydown") {
var orig_listener = listener;
listener = function(event) {
var suggestion_selected = $(".pac-item-selected").length > 0;
if (event.which == 13 && !suggestion_selected) {
var simulated_downarrow = $.Event("keydown", {
keyCode: 40,
which: 40
});
orig_listener.apply(input, [simulated_downarrow]);
}
orig_listener.apply(input, [event]);
};
}
_addEventListener.apply(input, [type, listener]);
}
input.addEventListener = addEventListenerWrapper;
input.attachEvent = addEventListenerWrapper;
var autocomplete = new google.maps.places.Autocomplete(input);
})(pac_input);
</script>