Hello David
You can certainly take your newly rooted plumeria outside at this time. If your nights are still around 8 degrees, you may want to place them close to the house where they are a little protected. In any case do not leave them in those temperatures if it rains.
You can certainly see flowers the first year. But this is no guarantee!
Once you start to see good new growth I would go ahead and fertilize them with a well-balanced fertilizer.
Show us a picture if you get a chance!!
