Trucks or Buses Left Lane Only. Does that mean me?

The posting for "Trucks or Buses Left Lane Only" can be for many reasons. It's generally because there's road construction. The right lane may be too narrow to accommodate wide vehicles. Or it could be slanted or doesn't have a base strong enough to support heavy vehicles like trucks or busses. As previously mentioned I would drive in the left lane when asked to unless you are exiting to the right. I don't know if you're breaking the law, but it's most likely the left lane is more conducive to large heavy vehicles.

It is the size and weight they are worried about. Sometimes the shoulder of the road is not as heavy duty.

If you are preparing to turn right you should be in the right lane regardless of what you are driving.