ClassiPress has an advanced search functionality which allows you to search by location based fields, and this is shown in the category view sidebar on the
ClassiPress demo site. It would require customization on your part if you were looking to move this to the main search, and how "easy" this is, would ultimately depend on your level of coding knowledge, as it's not a setting you can change from within the theme settings. ClassiPress is not encrypted though, so you are free to modify it as you wish. Thanks.