Lin, I agree with Gigi that there is no good solution for the rust problem on plumeria. Except! I have one in the back yard that gets a lot more rust than another one in the front yard. The only difference I can see (as they both get the same amount of neglect from me) is air circulation. The front bed outside our high fence gets a nice breeze along the street in the afternoons. It's even (sometimes, almost) cool enough to work out there in the afternoons in summer, thanks to the breeze.
So, just look at planting it out somewhere that the breeze blows really well in the afternoons, and that will dry off the leaves from summer rains. Then you MUST restrain yourself from planting tall stuff around it . . . . I pay little attention to the beds out front, and that's the only reason that plumie has lots of space around it still. The Spanish needles all around it aren't tall enough to impede the breeze . . .
The other thing to do is, when you visit the plant, be brutal about 'housekeeping' - take off any leaves with rust on them and put them in the trash so the spores don't spread. If you let those leaves fall to the ground, tons of spores fly.