Replace WP dashboard and admin bar font with your own (optional) locally hosted font. NOTE: I've used Roboto to match my theme, but called it Open Sans. This prevents error for admin plugin dependencies that expect an Open Sans style to be registered. WHY: If I'm doing local development offline page loads were always delayed by the Google Fonts …

functions.php

<?php

// Reregister Open-sans as Roboto.
function replace_open_sans() {
	// Replace the URL with your local or remote css
	$roboto_open_sans_url = get_template_directory_uri().'/assets/fonts/roboto-hack.css';
	wp_deregister_style( 'open-sans' );
	wp_register_style( 'open-sans', $roboto_open_sans_url );
}
add_action( 'admin_enqueue_scripts', 'replace_open_sans' );
add_action( 'wp_enqueue_scripts', 'replace_open_sans' );

roboto-open-sans-hack.css

/* Using http://www.fontsquirrel.com/tools/webfont-generato */
@font-face {
	font-family: 'Open Sans';
	src: url('roboto-light-webfont.eot');
	src: url('roboto-light-webfont.eot?#iefix') format('embedded-opentype'),
		url('roboto-light-webfont.woff2') format('woff2'),
		url('roboto-light-webfont.woff') format('woff'),
		url('roboto-light-webfont.ttf') format('truetype'),
		url('roboto-light-webfont.svg#robotolight') format('svg');
	font-weight: normal;
	font-style: normal;
}