By using Google Web Fonts can/does Google
Google can for sure count your users and track their IP address, browser version, and such. It won't be able to access user cookies as the font resides on a different domain.
By using a web font you are not sharing any content with the font provider, but your users may be providing a referrer address to the provider (the URL of the page containing the font request, i.e. using the font). If your page is public and does not require authentication, nothing prevents Google from reading this referrer, except best practices. If it requires authentication, then Google should not be able to get the text.
Google answers this question in their Google Fonts API docs.
To paraphrase the essential info:
"The Google Fonts API is designed to limit the collection, storage, and use of end-user data to what is needed to serve fonts efficiently."
"[...] requests for fonts are separate from and do not contain any credentials you send to google.com while using other Google services that are authenticated, such as Gmail."
"The font files themselves are cached for one year [...] When millions of websites all link to the same fonts, they are cached after visiting the first website and [the] result is that website visitors send very few requests to Google:"