A few years ago it rained for three days. On and off for two but all day while we were at the port of Cozumel. It POURED. The streets were a foot deep in water. BEST DAY OF THE CRUIES! No kidding. I can't explain why it was fun but it was. Maybe because it was different than the usual sun heavy days. We were given rain ponchos as we left the ship to keep us dry but even with the protection we got drenched. Now, having said all that, it is a warm rain, refreshing. It was almost like being a kid again, playing in the puddles. None of the rain bothered us, there is always something to do. Was it still worth it to us? Absolutely however we were on a 14 day b2b. If you were on a 7 day or even a 3/4 you may not feel that way.
And yes, we have had days that were forecast with rain and the rain never showed.