mjramon!
Both plantladylin and tarev gave you good advice. As soon as your plumeria starts to break dormancy (the tips start 'glistening' and/or new leaves appear) is the best time to step the plant up to a bigger pot. Always make sure your mix drains well (I add about 1/3 perlite to any good potting soil), and at that time you might want to add a well balanced time-release fertilizer.
Happy growing!
