I want to know how well it works with accessibility concerns of various and sundry natures.

You can try it out here: https://www.google.com/recaptcha/api2/demo

If you are a recognized as human you could perhaps try it via Tor.

I wish these google pages wouldn't automatically assume you speak some language based on your IP address - I get mine in German without any option to switch. Aren't there standards for setting language in web browsers?

Your browser sends an "Accept-Language" header with the list of languages and order of preference you have configured.

Sure, but many sites including Google like to ignore these (or at least have done so in the past).

The rationalisation is that users don't change settings like these, so their location is a better indicator than what their browser thinks.

> Aren't there standards for setting language in web browsers?

Yes, the Accept-Language HTTP header.

I'd assume that where cursor tracking is unavailable, this experiences just degrades to a standard CAPTCHA as depicted in the post.