I've got allergies to pollen and used to get a sinus infection every spring and fall.

I found that my susceptibility to infections were reduced by:

1) Don't take aspirin or anything similar that thins the blood. It makes it easier to get nose bleeds and end up with scabs and so forth in the sinuses.

2) Consider hyposensitization shots. It helped me a great deal, though I still need to take ~ 1/3 of an Allegra D every morning when the pollen count is off the chart.

I haven't had a sinus infection in a long time (2-3 years?) since I started doing these things.

Luck - especially with the surgery!

Cheers,
Scott.