Use the following snippet to load jQuery from a local file, into your WordPress footer, if it fails when loading from your CDN of choice.

function inline_footer_scripts(){ ?><!-- LOCAL JQUERY FALLBACK -->
<script type="text/javascript">window.jQuery || document.write('<script src="<?php echo get_template_directory_uri(); ?>/js/jquery.1.7.1.min.js"><\/script>');</script>
<?php }
add_action('wp_footer', 'inline_footer_scripts', 1);