PVC tubing is a great Idea. I used some 1.5" tubing as a temporary fence to keep my parents dog off the grass when I have him for extended periods. I just dug a 12" peice of 2" tubing into the ground as sleeves and then drop the 1.5" posts into them. I then zip tied some plastic fencing material to the posts. When I no longer needed the fence I simply pulled the posts out of the sleeves and rolled it up for use the next time they drop the dog off. I had some rubber caps that covered the sleeves to keep the kids from filling them up with dirt/sand etc. It worked great.
