Me and my three friends are coming in another week. But our friend just returned from there and it rained on them all week. What is the weather like.

My wife and I have been to the Cancun area many, many times, al throughout the wear. You must be aware that Sep. thru most of Dec. is the wet (Hurrican) season. I will rain often, sometime daily. That is one of the reasons the cost is generally more reasonable.
We always use a travel agent. Good agent will warn you of negatives. We have never been disappointed because we knew what to expect.