Have you tried applying Fungionex before the start of the leaf out season? You may need to do this for a few years to get the fungus under control. I would also investigate reasons/causes why it is so easy for the fungus to spread in your garden.

Well, I talked to my local Experiment Station and they said it could be an issue of air circulation ... which should be better in the new site. They also said that some cultivars are just prone to these. And we had a LOT of rain this year, making for damp conditons (still, the Weston is the only one that gets these).

Having said all that... the scent from the blossoms on this azalea simply cannot be compared to anything else! It's in front of the house and I can smell it through every window! I won't give it up without a fight!

I guess my question was really about cross-infection: if the Weston is prone to the galls, and I follow your advice about spraying (or even just religiously inspect and hand-pick), can I protect the others (Robin Hill Gillies and a rhodie) from this fungus? Are the Weston's particularly prone to this? I just picked a few new galls (VERY small so glad I found them!) off today, so I am not overly optimistic, but perhaps the damage is already done for this year and I should look to see how it performs next year.

I would spray them... all who are close... so this does not become an annual required gardening chore. I have not seen Weston's Innocence in a list of susceptible shrubs that suffer from gall. Try never to overhead water these shrubs as yet another way to minimize chances of getting the disease next year. The fungus likes to overwinter on new leaf buds so apply the fungicide now and increase air movement between shrubs to help limit this problem in future years.

From Cornell University:

Azalea gall is a problem of widespread occurrence in this country. Pale green, pink, white, or brown fleshy galls, caused by the fungus Exobasidium vaccinii, may develop on leaves, branch tips, flower parts, and even on seedpods. 'Pinkster apples' is a term applied to these abnormal growths by those who enjoy them as a food delicacy. Exobasidium vaccinii also infects species of Vaccinium including cranberries where it produces bright red, swollen spots on the leaves and fruits. Infected stems become thickened.

The fungus overwinters within the infected plant. In late spring and early summer, a whitish coating appears on the swollen plant tissue. This coating is composed of many microscopic fungal structures that produce spores capable of infecting more plants during moist weather. This disease is not usually a serious problem unless wet conditions prevail for long periods of time.

To control this problem, the galls should be hand picked and destroyed before they turn white. Most native and horticultural azalea and rhododendron plants are susceptible. Some species and cultivars are more susceptible than others. Rhododendron maxium L., R catawbiense Michx, and their hybrids, are listed as being particularly susceptible, as are the Indica azalea group. Susceptible plants growing in poorly aerated soils are more subject to infection by the fungus than those growing in well-aerated soils.

From NC Extension:

Leaf gall is common in azaleas in the springtime. It is caused by a fungus and, while unsightly, is fairly harmless. You can control leaf galls by removing the diseased leaves. D.M. Benson and Tom Creswell of the Plant Pathology Extension, North Carolina State University, recommend removal rather than a fungicide because of the low rate of damage caused by leaf galls and the ease with which the infected leaves can be disposed.