[xgarb]

Here's a test for a basic install..

http://yellowlab.tools/result/eo09vuo23z

showing 30 fonts http://yellowlab.tools/result/eo09vuo23z/rule/fontsCount

I'm pretty sure that these are loaded as one file by the browser but there's still the bandwidth to consider. Although there is this Our cross-site caching is designed so that you only need to load a font once, with any website, and we'll use that same cached font on any other website that uses Google Fonts..

I see this in the header:
<link href="http://fonts.googleapis.com/css?family=Open+Sans%3A300italic%2C400italic%2C600 italic%2C700italic%2C400%2C300%2C600%2C700&amp;sub set=latin%2Ccyrillic%2Clatin-ext&amp;1487706193" rel="stylesheet" type="text/css" media="not print" />

which must be coming from

'Open Sans:300italic,400italic,600italic,700italic,400,300,600,700')
                        . '&subset='
                        . urlencode('latin,cyrillic,latin-ext'

The site doesn't need Cyrillic or latin-ext characters and the italics can be simulated (and are possibly cached anyway) so I would just use 300,400,700.