I'm glad you realize that they aren't bad to have around, and I hope that you don't kill them. They are very important for insect and rodent control. Get rid of snakes and in a couple of years you'll have more bugs, mice and rats than you thought possible. There are snake repellents that can work, but if I were you, I would try to remove any habitat or shelter near the garden so they move farther away. If they are hiding under a shed or nearby house, it's going to be hard to keep them away. They like to live under mulch and compost piles, building rubble, rock piles, stacked wood--places like that--so move those kinds of things away from your garden. Keep the grass cut short all around the garden for several feet--tall grass is a good place for them to hide.
They scare me too, but mostly because I don't hear them coming and all of a sudden they move and make me jump. Think of them as lizards without legs, and remember how great they are at keeping bugs and rats away.