HTML多级表单

I have some trouble making a search form that can be used for real estate. The user should type/select a city or can just type/select his region or country for wider search results (estates from the whole region) as shown below:

It can be done with <select> <optgroup> <option> but <optgroup> is not clickable and I have a lot of data (2700 cities), so Ajax/Jquery is probably the best way to do this.

Are there any plugins/ways to help me achieve this with just one form input?

May be "Chosen" jQuery plugin http://harvesthq.github.io/chosen/#optgroup-support (optgroup paragraph)?