[Image description: a 72 cell seed starting tray filled with a mix of coco choir, vermiculite, and worm casings, next to a line of 12 types of broccoli, cauliflower, and cabbage seed packets, all but one from Baker Creek.]
Baker Creek has good seeds except they are, without basis, completely anti GMO and pro organic. Propagandizing their seeds as making 'pure food'.
Plus being seventh day Adventists they closed their seed bank on Saturdays.
But their seed catalog is pretty much the best
Depending on the zone you're in yes. I'm in 9b and rarely get freezing temperatures, so I can grow things over winter that might not survive in colder areas. Some brassicas are especially frost tolerant, so it would be worth looking into and seeing what you can grow in your area.