I have about five (5) Hampton Bay fans that uses a Remote Control to turn On/Off the light (9-inch round tube), and to turn On/Off and control the speed of the fan.
However, I've been having trouble with the remotes operation.

The question is:

Can these fans be "converted" so they can be operated with the regular wired dimmer/light switch combination?

If yes, where can I obtain a wiring diagram to make the changes?

Some fans can and some can't. Have you tried contacting Hampton Bay?