Gravity forms integration with epl data

Hi Merv,
The Gravity Forms support team got back to me and said to use Example one from
http://www.gravityhelp.com/documentation/gravity-forms/extending-gravity-forms/hooks/filters/gform_pre_render/#example-1

Which is to use this code…but I’m not sure what to change to make it work for property listings.
To clarify, I want my form here
http://raindancedev11.com/contact-timeshare-hawaii/buyer-contact-form-listings/
to work like
http://timeshare-hawaii.com/buy.html

So it seems like I’d have to make 5 different drop downs, one for each island, and put the details from the shortcode below into the php code they show in the example…but not sure what to put where?

[listing post_type=”property” status=”current” location=”oahu” sort_order=”ASC”]

<?php
add_filter( ‘gform_pre_render’, ‘populate_dropdown’ );

//Note: when changing drop down values, we also need to use the gform_pre_validation so that the new values are available when validating the field.
add_filter( ‘gform_pre_validation’, ‘populate_dropdown’ );

//Note: when changing drop down values, we also need to use the gform_admin_pre_render so that the right values are displayed when editing the entry.
add_filter( ‘gform_admin_pre_render’, ‘populate_dropdown’ );

//Note: this will allow for the labels to be used during the submission process in case values are enabled
add_filter( ‘gform_pre_submission_filter’, ‘populate_dropdown’ );
function populate_dropdown( $form ) {

//only populating drop down for form id 5
if ( $form[‘id’] != 5 ) {
return $form;
}

//Reading posts for “Business” category;
$posts = get_posts( ‘category=’ . get_cat_ID( ‘Business’ ) );

//Creating drop down item array.
$items = array();

//Adding initial blank value.
$items[] = array( ‘text’ => ”, ‘value’ => ” );

//Adding post titles to the items array
foreach ( $posts as $post ) {
$items[] = array( ‘value’ => $post->post_title, ‘text’ => $post->post_title );
}

//Adding items to field id 8. Replace 8 with your actual field id. You can get the field id by looking at the input name in the markup.
foreach ( $form[‘fields’] as &$field ) {
if ( $field->id == 8 ) {
$field->choices = $items;
}
}

return $form;
}
?>