As was reported yesterday, it looks like the Sprint Galaxy Nexus will, in fact, be receiving its upgrade to Jelly Bean. Finally. According to documents on Sprint's support page, the JRO03R build starts rolling out today. It looks like it will be an OTA update. If you want to compulsively check for it, though, you can do so in Settings.
We're still waiting to see if the Nexus S 4G will also get the promised Jelly Bean update, as we'd also heard.