Publish in different countries at the same time ?

You should get one agent, in one country. That agent then would take care of domestic sales (so, sales in the US if you have an American agent) and foreign and translation rights too (which means sales to publishers elsewhere, whether they're in English or any other language).

Very few agents will want to take on a writer in the way you describe. It would mean that potentially, you'd have two agents both trying to sell your book into the same territories, which is not good.

Further, it's extremely unusual for an author to translate his or her own work even when the author is completely fluent in both languages. Pubilshers buy foreign language rights and use their own translators. So you might be doubling up on your work unnecessarily.

Of course you know when your books are being translated! A good agent keeps her author-clients informed of everything; and can't sell rights to your books without your agreement.

The countries are chosen by your agent (or her sub-agent in other territories) depending on where she thinks she can sell your book, and where she has good connections with publishers. Some agents don't sell much in the way of foreign rights: perhaps eight or ten foreign rights deals per title are good-to-middling, but the better agents routinely make twenty or so foreign or subsidiary rights deals per title.

An author can always talk to his or her agent about where they'd like the book to be published, and how. None of this should happen without your input.

My multi-national books have all been non-fiction, but the basics are the same. One agent who will negotiate rights for local and international sales, or partner with international rights agents as needed (most do). You need a single point of contact and coordination and, if you're using an agent, that's the agent's job.

My contracts have all spelled out translations and foreign sales rights and, in my case, it's been the same publisher. They handled everything and kept me apprised of timelines, as well as sending me author's copies of the translations. It's always fun seeing your name in Chinese, even if you haven't got a clue what the book says.

Keep in mind that, depending on what you write, there may be no significant market in some regions. My books, for example, have never been translated into French because every French-speaking reader in the market place would also be able to understand the original English version.

Jeff