You have the Captain Cutlass sword avaliable! All you have to do, other than pay
about 11,000 dollars, is give Ivor some money. Does some stranger (Ivor) ever walk into your garden? Well, if you give him enough money he'll open a shop for you! In that shop you will find a sword called Captain Cutlass. Simply just put it in your garden and you will have no more worries of viva pinata Ruffians again!
Some other ways, if you don't like spending 11000 on a sword, is to brib them with money. Press "x" on your controler then pay him. They are greedy, so pay a lot.
Another way, so I've heard, is to get a Dragonache in your garden. But that only prevents Profesor Pester.
*In my opinion, Captain Cutlass is the best thing to "tame" the viva pinata ruffians.