No, not directly. As with other forms of advertising, it would be frowned on by every stack exchange site I've used.
However if you are participating in a meta discussion anyway, and the subject comes up, I see no problem in mentioning that this proposal exists in passing.
This happened a lot on Stack Overflow, when we were trying to get Programmers created, and again on Programmers, when we were trying to get Workplace created. In these cases people would say something like "This question is off topic here, but is good-subjective and would be a good fit for the proposed X site".
So, I would suggest hanging around on the sites you mention, participate in the site building activities of those sites on meta and mention this proposal if and when the topic comes up. Be subtle about it and no-one will raise an eyebrow.
No, I'm sorry. I can appreciate your need to find a community for this proposal, but that type of solicitation would not be appropriate within our existing sites. With the number of proposals that go through this forum, it would simply become untenable for our existing sites.
Our communities are already aware of Area 51. It is better to try and draw a community that would expand our existing network, and not just chop it up into smaller pieces.