Which caterpillar do you have? Some, even some that live on Hibiscus, will eventually turn into butterflies.
Anything that you could spray that would deter them would also kill them.

I understand that spraying a deterrent could kill them by eliminating their food source. However, what I plan to do is spray a deterrent on some buds/stems that I want to save, and leave a few sacrificial ones for them to munch on. I would certainly like butterflies in my garden, but not when it means the loss of so many flowers (more than 50% bud loss at the moment). I have reason to believe that they may be moth larvae, since most of my other flowers are not yet in bloom.

Enoughcliches, you certainly have the right to protect your ornamentals against destruction. I wonder, however, if you've seen this actual culprit, or if you're assuming that it's a caterpillar or grub.

A good description (or better....an image) of your pest or of the damage would be helpful.

In the meantime, I'll suggest Neem oil. It works by preventing insects from feeding or boring. It's effective against against a wide variety of insects, and may prevent further damage to your plants.

Avoid spraying on blossoms, however.

Keep in mind that Neem is a broad spectrum poison that wil also kill any beneficial insects that contact it. The best way to use Neem is as a spray directly on the target insect.

Neem actually works by preventing feeding and not as a contact killer (except for eggs and nymphs of soft bodied insects). Remember, it's a common ingredient in health and beauty products (for humans).

However, it should not be used on plants indiscriminately. Though it's considered much safer than most organic products on non-target insects, there is still much that is not known about the chemical pathways that it might affect in the insects.

For example, using Neem oil on as a preventative (smother eggs and nymphs) is very effective, but it 'might' also prevent the all important parasitoids from doing their work (though neem doesn't kill them outright).