Gigi, I'd think you would do well with Spathoglottis the same way you grow your Dendrobiums, alongside the plumeria. I haven't had any luck growing Spaths in ground here, but I do have a lot of oak tree roots to contend with. So all my Spaths stay in pots. They'd help fill in the flower gaps, especially great at this time of year.
Under a deciduous shrub like your plummies, they'd get some nice shade in summer, and lots of sun in winter which should be just right for them. That's what mine get anyway.
Watch for them on sale at Lowe's - they get different colors all through the spring, and boy! do they ever fly off the shelves fast.
