Our first trip in our new popup was 10 days in late July 2001. It rained 9 of those days, 3 of the days was almost nonstop. (There was a tropical depression in the gulf)
We had a blast.
Be sure to bring a tarp, rope, and extra stakes for extra rain protection. Bring a roll of Quarters for the dryers. Bring your ponchos and extra clothes, especially socks and shoes. Most importantly bring a good attitude.
Wait and take advantage of any breaks in the rain to set up camp. Don't try to set up during a steady rain. Sounds like common sense but you would be surprised how many people I have seen work in a poring rain and get everything soaking wet only to have the rain stop or get very light just as soon as they finish.