mirrors

I don't use one, but if I did, I'd only have one for the left side (for U.S. roads). As you get more comfortable on the bike, you'll be able to move your head around with more confidence (assuming you go without a mirror). You don't need to turn your head all the way around...turn your head slightly and use your peripheral vision to check for overtaking traffic.

I don't use mirrors; I glance quickly over my left shoulder when I need to look behind me. If you do feel you need to use a mirror while you get comfortable on your new bike, I think left only is the way to go. All of your traffic will be on the left; upcoming cars or other cyclists passing you.

As far as falling over clipped into your pedals, I think everyone has done that at some point. If this is your first time riding with clipless pedals, I recommend you go to a parking lot and just practice clipping in and out of your bike. Practice unclipping one foot as you slow down and lean the bike to that side as you stop. Then practice clipping back in quickly as you restart...this is an important skill to master as it will make riding on the road much safer.
-john