Just returned and am updating with info from my experience.

Garuda Indonesia
- No seatmap in Delta online tool.
- Obtained Garuda conf. number from Delta and used on Garuda website to "manage booking". Website says my ticket (discounted Y) was "promotional" and not eligible for seat selection until check-in.
- In Bali I visited the Garuda office at The Bali Collection and was told same.
- On a whim, I called the Garuda main office (62 21 2351-9999; within Indonesia I called 021 2351 9999). Select English -> Frequent Fliers -> Sky Team Elite / Elite Plus. The phone agent verified my Sky Team Elite Plus status (using DL FF number) and happily selected nice seats for my wife and me. These "stuck".

Three additional notes:

1- Some discount Y tickets are not allowed online check-in until 12 hours prior to departure on the Garuda website. Since they use 24-hour time, it can look like you should be able to check in ("You will be able to check in at 12:25") when it's 12:30am and you've waited up. It will take a while to figure out that if they meant 00:25 they would have said that.

2- On the A330-300 they fly a 2-4-2 in Y. The "2" seats at the bulkhead on either side have _no_ legroom. The "4" have decent legroom, but nothing like the bulkhead A330 on other carriers.

3- Garuda seems genuinely excited to be part of Sky Team. They talk about it everywhere, have a special check-in counter in the back (in addition to Sky Team Elite lines), lounge access, etc.