The caffeine in coffee does in fact dehydrate you. You may not notice the effects since you as a cyclist know to also drink copious amounts of water as well. This is most likely offsetting the dehydration effect of the caffeine in your coffee. If it's been working for you so far I wouldn't sweat it.

Also, if you're really concerned, take a look at the color of your urine the next time you have to relieve yourself. The general rule of thumb is that if your urine is clear, you're hydrated. If its a yellowish color you're on your way to dehydration. And if it is a deep orange and it smells like urine...you're dehydrated and you need to drink water.

I also drink coffee just about every morning and find that my first urination after drinking my usual 2 cups of coffee is clear, however the 2nd urination is a yellowish color. I drink some water and i'm back on my way to clear urine and decent hydration.