I would suggest moving it up in pot size more gradually. I hav heard of plumeria rotting if they are moved into a very large pot too quickly. I move mine from 1 gallon size to 5 gal to 15 gal as they grow. Look for roots emerging from the drain holes as a sign the plant needs a larger pot. The plant should get thicker as you move it into larger pots. I have to admit there are growers who put them into the larger pots right away, but most of the growers I speak with in CA use the stepwise method above.
As far as blooming, plumeria bloom when they feel like it. People advise using a "bloom enhancer" fertilizer which has a high middle number. The miracle grow seems to have that. Plumeria branch when they bloom, with the new branches developing at the base of the bloom stalk. You can force branching by pruning the tip of the plant. New branches will form at the cut tip. However, this will delay blooming because blooms (inflorescences) develop only at the tip of a branch. Pruning will keep the plant a manageable size. I try to prune mine to keep them fairly symmetrical, then root the part I have cut off to make another plant.

Go to plumeria101.com. They have a great amount of information for plumeria care.

Mike

Ditto to pretty much everthing Mike said, but the regular miracle gro encourages leaf growth whereas a bloom booster provides the nutrients to encourage flower development... I use Miracle Gro Bloom Booster which is a 10-52-10, a much higher middle number... plumeria also need light and warmth... if it's not getting enough of either then it also will no flower... the warmer the better... I live in Phoenix and we don't lack for warmth... I kept a few of mine in the greenhouse for winter to encourage growth and blooming and was regularly hitting 90-100 and one of them has an inflo... that's not saying that you NEED really high temps, but they come from a warmer weather climate and thrive on the warmth... I would be careful pruning yours right now... how many arms does it have?? If only a couple then I wouldn't recommend it, and if it has no arms I wouldn't prune it until it has branched... and like Mike said, your blooms come from the growth tip so you will severely delay blooming if you cut it off... I hope some of this helps... also realize that some cuttings are more stubborn than others... what kind of plumeria is it, do you know?? Good luck and feel free to ask more questions... and plumeria101 is a great site
Brittany :)

I have several Plumeria in pots but they have only one central trunk with several branches at the very top. I have to bring them inside for the winter as I live in Las Vegas, NV and it gets to cold in the winter. I have them in a mostly shaded spot and bury them in the ground outside in their pots for the hot 105+ weather for the summer. My problem is they are getting to tall to easily bring inside and then back outside but I am afraid if I just lop off the top to make it shorter the plant will die. Can someone please tell me the best way to make it shorter or do I just have to have it get taller and taller. If it had forks lower it would be easier but they are all right at the top which also makes it very top heavy.