I do not know how to get rid of them, but if you use a spray, make sure you have on protective gear (even over the face...get some netting from a fabric store, drape it over a hat and pack into your shirt). They will fly in all directions during the day, but I do know they will congegate at their hole in the ground near dark, so you should be able to pin point where to attack. You will probably be able to google some info on this.

Dealing with Yellow Jackets should be a job of a pro. There are many chemicals sold over the counter that can do the job, but if your not really sure where they are located, or concerned about getting stung the cost of your safety is well offset by having someone who does this type of work for a living. Properly treated the nest will be rendered useless with no harm to you or the area around you. Do it wrong yourself and the stings these insects can cause can put you out of commission for ...»

We use traps sold at Home Depot - they are called "Yellow Jacket Traps" :) They work really well .. nearly eliminating the problem, but we do have to treat it every spring/summer with new bags. Basically they are bags of sweet stuff that they get in .. and cannot get out.