They most likely will not flower
unless you give the roots enough room to grow. They also need at least 6 hours of direct sun during summer. If you keep them indoors, I would suggest a grow light, like many who live in colder climates use. Otherwise they will just grow very tall and skinny, usually do not branch out, and probably won't develop flower
stalks - commonly referred to as "inflos".
I really suggest putting them outside, until night time temps reach down to below 45F.
If you are into Facebook, there is a terrific group called "Plumeria Growers", which is a great resource for all sorts of information about plumerias.