if you are downwind from gmo's you are likely going to have to watch your planting dates, so that your plants are not receiving pollen at the same time as the gmo plants near you.
I'd keep a diary of when they plant..and when they harvest..or discuss it with them, maybe they can tell you their plant and harvest dates and number of days to harvest on their seed..then try to pick a seed that has a different number of days and plant them either earlier or later so they do not coincide with the gmo plants.
in most areas the biggest problem is likley corn.
you can see when they are preparing their fields for planting and get yours in before they get theirs in, and get a short season corn..or wait until theirs is in and planted ..and plant a few weeks later..if you have a long enough growing season..my guess is earlier is better if you can get yours in and harvested first.
Bloom where you are planted.
Location: Portland, Oregon Maritime, temperate, zone 7-8.
GMO Canola is very promiscuous. Studies in the major U.S. growing region show that the wild plants growing along highways many miles from the cultivation sites have been heavily contaminated by the GMO version. I have heard that the wild version will soon be extinct in Montana due to this cross contamination.
If the GMO stuff they're growing is canola, then surely it won't cross with your brassicas? I know brassicas readily cross with each other, but as far as I'm aware there's not much chance of them cross pollinating with corn. Unless anyone knows differently...