Wow. If they don't look nice as just a tree, I'd probably take a cutting off each (as it will still bloom and take less space) and get rid of the trees to make room for something that will bloom.
I've got a few 12-15 inch cuttings that bloomed last year for me and I'm sure they'll bloom this year too.

Sometimes the problem for a Plumeria that doesn't bloom is simply a matter of the size of its pot. As far as I know, a mature Plumeria needs a two gallon pot.
If your Plumeria seedlings are taller than 50 cm (hmm, that would be about 19 inches or 1,6 ft. in America :) ) and have pots smaller than 2 gallon, a simple transplant to a larger pot may give you a surprise perhaps this very year, 'cause it's not too late to re-pot them now. Also give them fertilizer to encourage new growth.

I know of someone in Florida who did just this last year and her 5 year-old never bloomed before Plumie had her first inflo last summer!

If this is not the problem, perhaps you don't give them too much sun?

Maybe if you give more info on their condition I might be of some help if it's not too late. I wouldn't give up on them, unless you have other grown Plumerias that do bloom.

Good luck!

Just curious....How tall are they?
Are you using a fertilizer with a high middle number? If not, try that.

Brighty

I started growing seeds about 10 years ago
I start the seeds in one gallon pots;
the next year i put into five gallon pots
for as long as i have them
I use 20-20-20 and 10-50-10 plus whatever else i can find to throw in there
The older ones are almost seven feet tall;
this time of year they look like big broomsticks
I generally have between 80 and 100 trees
My idea was, as I get older, to scale back to just a few that no one else has
So far I have eight, none are "show-stoppers"

Are you saying some are seven feet tall and have never bloomed? Yickes!

Brighty

up to seven feet AND up to ten years.

well what do you know
cancun pink seed planted 5/15/02 flowered
it's yellow with faint pink band on edge of petals
i'm six feet tall looking up at it.