Yes, most cats are not fond of leashes, as they are much more independant and leash training should be started from an early age. As far as the leash laws, they mostly are for dogs, while cats are usually under a "containment" law (meaning they must be contained to your property- not that most outdoor cat owners abide by this).
There are cat fences that prevent cats from climbing over the tops. Purrfect Fence, Affordable Cat Fence, Cat Fence-In, are a few names of these products. There are a few plans online to make home made versions of these too.
What about covering your flower beds with rocks, instead of mulch? This technique is used for indoor potted plants to prevent cats from digging in the pot. Cats prefer to dig in sand/dirt/litter, but not rocks.