I am in South Texas where it is just as likely to be 80 deg in Dec and Jan
as it is 40 deg., and some years we have only a few really "cold" days where
it reaches 32 deg. I need to take a bunch of branch cuttings from a
frangi-pangi so that it will encourage it to branch out better. But in
another month it will probably drop its leaves (its still green growing
strong now). Should I take cuttings and start them rooting now, or wait
until next spring?

hi there
take plumeria (frangipanni) cutiings at any time of year.
when you give them time to dry out all leaves will fall off anyway, so it matters not if it is leafy or leafless.
take care
Renay