I have noticed ants on my tropicals also. One expert told me to watch very closely for aphids (that when a lot of ants are present you probably have aphids)Sure enough I noticed the little buggers on some of the buds. I treat with a soap and water mixture (with a little oil mixed in for adhesion). I am fairly new to the tropicals, but hopefully this will help. Good Luck!
Claire

Fireants love my Tropical Hibs!!! This year I have almost no fireant colonies popping up in my yard but I'm on and off fighting them in and around large containers that sit on ground. I use Amdro for control for fireants.

I've read that "regular" ants "tend" to aphid herds. I think it is for "cultivation" of aphid dew, but not sure.
geekgranny

Yup ants are there because of some other insect pest which produces a honey dew (which is really bug pee). Most likely it's aphids. A soap and water spray with some horticultural oil (dormant oil for fruit trees) mixed in will help. Pruning back severely affect tips helps too. I've attached a link to some interesting recipes. Just be sure to try on a small area first in case your plant has a nasty reaction.

Rolande in Ottawa Canada

Here is a link that might be useful: bug spray recipes