When I lived out in the country, I had the same problems...
Bungee cords over the garbage cans helped most of the time, but they still got in on occasion. We ended up trying ratchet straps, but the little suckers chewed through them. Finally, I put two locks on it like the ones you put on a shed door and use with a master lock. They never got through those and instead of a master lock, I just used extension cord clamps since they're easy to remove (for humans!).
As for the snakes, you could try mothballs. That seemed to work for me. But after i ran out, I was kind of lazy, so I sprinkled some granulated chlorine (for pools) between the cracks of the deck. It killed the weeds that were growing up through the deck too. Of course, it smells like chlorine for a few days and it'll kill your grass if you use too much and there's run-off. But I had rock under mine and it all sloped towards a patch of rock that surrounds the pool so i didn't worry about grass issues. And it may not be too environmentally friendly, but it worked well. (And the snakes never came back... Neither did the racoons, skunks, squirrels, and other critters.)
While I know these are proven methods, just be careful with the chemicals and the amounts you use. I'd hate for you to kill your lawn or have chlorine fumes choking you to death as you try to enjoy your deck. Remember... A little goes a long way... Animal senses are far more sensitive than our own...

