I don't see any jobs listed that are specifically remote. To apply as a remote developer evangelist, would one need to simply apply for, say, the SF one?
Yes. Our Taleo system doesn't have Remote as an option but I'm very happy to talk with remote candidates and in fact my dev rel team right now is 100% remote.
That's going to depend on the role, the hiring manager, and the candidate. I can't answer for all those but I'd suggest it's always worth a conversation if you see a role you find really compelling.