Removing "Zip Code" option in search bar and replacing with "Cities" instead

So I have the Classifieds Blue child theme for my website (www.lakomai.com)… I’m wanting to remove the “zip code” option in the search bar at the top of the page, and replace it with a drop down menu of “Cities”… Anybody have experience with this?

I require users to give the “Item Location” whenever they post an item for sale, So I figured that I could somehow use that Db Key of “item-location” to create the drop down menu in the search bar at the top of the home page…. I have a little bit of coding experience… enough to “tweak” things… but not really enough to create huge globs of code… any help in this area would be awesome!