If you don't want to set up and install a fence (which can get pricey), have you considered about buying 1-2 X-pens (tall ones of course) and putting them side by side so it makes a giant rectangle? The X-pens are about 8 panels so two of them would be about 16 panels and it would cover quite a bit of your yard. They're pretty cheap on Amazon--(
Amazon.com : Midwest Black E-Coat Exercise Pen,... ) , about $28.79 for a 24x24 (but this is kind of small. it depends on how high your yorkie can jump). But I would also keep a VERY close eye on her. Make sure that she knows her name and responds well to "Come" just in case she jumps out. Either that or use a retractable lead so if she jumps out it might be easier to grab the lead, instead of her.
