I agree with the others. Putting the best tires on the rear axle is safer than putting them on the front axle. However, before the dissenters chime in, let me play devil's advocate.
When you apply your brakes, most of the braking (usually about 70%) is done in the front. The other ~30% of the braking is done by the rear brakes. Therefore, expect your emergency braking distance to be a little longer if you put the worn tires on the front.
Generally, especially with front wheel drive vehicles, the front tires wear faster than the rear tires, so if your goal is to rotate your tires to have them wear evenly, it makes sense to put the good tires in the front.
However, if your goal is to be safe for now, and replace the two bad tires shortly when you have the money, put the bad tires in the front and the good tires on the rear.
The reason I make these points is to urge you to replace all four tires. It is really the safest option. I also urge you to slow down in corners and get your tires rotated with every other oil change.