Well, leeneia, I checked a few keyboards from Casio, Yamaha, and Roland. All have the round MIDI In/Out ports, but only one expensive Roland keyboard had USB. So, you'll most likely have to buy an adapter. The MIDI ports can be a bit troublesome, although the most common problem is confusing what "In" and "Out" mean - they're just the opposite of what one would think they should be. I don't know how many times I've made myself look like a genius by just switching "in" and "out."
The USB connection is almost dummyproof.
-Joe-