Eh. I can't say that I have a natural speed per se. I do have a very natural instinctive, burned in cadence, though. When I climb onto a bike and begin riding, it doesn't take long to lock in to about 88-92 rpms depending.

From there, it's just a question of gearing, how I'm feeling power wise, and whether I'm in a group or alone. Speed will be whatever it is. Now that I've become a regular commuter and I know exactly how far I must ride and how many minutes it takes, it looks like my riding speed is ~13.5 mph. That's over fairly hilly terrain, maybe 450-500 feet over ~8 miles. That, and hauling some clothes and food and stuff.