Jquery Ajax Email Signup Form in Wordpress

ajax.js

// This function will submit the mailing list form through Ajax
// No page load necessary!
$('#addressForm').submit(function() {
	$.ajax({
		type: 'GET',
		// This page will need setup in your wordpress admin, and you'll need to assign the ajaxServer template below. This way you have access to all the wordpress globals
		url: '<?php bloginfo('url'); ?>/ajax-server-do-not-delete/',
		data: $('#addressForm').serialize(),
\		success: function(response) {
			$('#response').text(response);
		}
	});
	return false;
});

ajaxServer.php

<?php
/**
* Template Name: ajaxServer Page
*/
?>

<?php
// run the function to submit the form data to the database
echo(storeAddress());
?>

form.php

<h4>Subscribe</h4>
<p>Sign up for our email list to stay in the loop on the latest happenings.</p>
<p>I use the site as...</p>
<form id="addressForm" action="index.php" method="get">
	<input type="radio" name="usertype" id="radFree" value="Freelancer" checked="checked"/>
	<label for="radFree">Freelancer</label>
	<input type="radio" name="usertype" id="radEmp" value="Employer" />
	<label for="radEmp">Employer</label>
	<input type="email" name="address" id="address" placeholder="email" />
	<input type="submit" value="Go" class="buttonGreen" id="emailSubmit" />
	<p id="response"><?php echo(storeAddress()); ?></p>
</form>

functions.php

<?php

// Function to store addresses in the database to be used later for the mailing list
// This should be added to functions.php in your wordpress theme folder
function storeAddress() {
	$message = "&nbsp;";
	// Check for an email address in the query string
	if( !isset($_GET['address']) ){
		// No email address provided
	}
	else {
		// Get email address from the query string
		$address = $_GET['address'];
		// Get radio selector from query string
		$userType = $_GET['usertype'];
		// Validate Address
		if(!preg_match("/^[_a-z0-9-]+(\.[_a-z0-9-]+)*@[a-z0-9-]+(\.[a-z0-9-]+)*$/i", $address)) {
			$message = "<strong>Error</strong>: An invalid email address was provided.";
		}
		else {
			// Connect to database
			$con = mysql_connect(DB_HOST ,DB_USER, DB_PASSWORD);
			mysql_select_db(DB_NAME, $con);
			// Insert email address and user type into mailinglist table
			// Here is the sql to create the mailing list:
			// CREATE TABLE `mailinglist` ( `id` INT NOT NULL AUTO_INCREMENT , `email` TEXT NOT NULL, `user` TEXT NOT NULL ,  PRIMARY KEY ( `id` ) )
			$result = mysql_query("INSERT INTO mailinglist (email, user) VALUES('" . $address . "', '" . $userType . "')");

			if(mysql_error()){
				$message = "<strong>Error</strong>: There was an error storing your email address.";
			}
			else {
				$message = "Thanks for signing up!";
			}
		}
	}
	return $message;
}

?>

SQL Query to create table

CREATE TABLE `mailinglist` ( `id` INT NOT NULL AUTO_INCREMENT , `email` TEXT NOT NULL, `user` TEXT NOT NULL ,  PRIMARY KEY ( `id` ) )