Some of the stuff I've read says there's no known interaction but that doesn't mean some people won't have a reaction. Personally I drink a lot of coffee and haven 't noticed a change in my INR.

You can also google it and see what comes up.

My doctor told me to limit my coffee while I on warfarin (1 cup a day max), but I didn't notice a problem at my normal consumption rate of 2 to 3 cups a day.

If you drink roughly the same amount every day, I don't know why it would be a problem. Your warfarin dose would be set to meet whatever adjustments (if any) that the coffee makes to your INR.

I'd say if you're not comfortable with just wining it, start drinking it regularly and check your INR to see if it impacts it I drank decaf probably the first month after my PE because I was still having a high heart rate which caffeine did nothing for, but once that settled down I switched to regular and it had no obvious impact to my INR. I also will go for a brief period where I don't drink it because it aggravates my acid reflux but once that is under control, I start drinking it again, and still notice no impact to my INR. Can't say it's the same for everything but it doesn't affect me at all.

And did I mention I LOVE COFFEE

I'm not worried about the caffeine as I drink pop like it's water. Always have and probably always will. That hasn't affected my inr at all. Recently, well before I started with this whole pe/dvt mess I had started drinking coffee and I now like it, especially gevalia and I want it so I suppose if everyone else is having it, I will too!

just make sure you have enough fluids and don't get dehydrated.

Someone showed me this list of food with their vitamin K content a while back, if that helps. It says it's low for coffee. I drink coffee a few times a week, and it's never affected my INR. I've never heard that it negatively affects it.
http://www.med.unc.edu/im/files/patient-education-handouts/nutrition-and-diet-files/Vitamin%20K%20%20Content%20of%20Common%20Foods.pdf