Really the problem is he's only got part of a full H-bridge, you should have an input for PWM and then either one or two inputs for direction control. You do still need two PWM channels for driving two motors though, so something like a 16F876, which is smallish and has two PWM channels is ideal. My PWM 'tutorial' is designed like this, and gives seperate PWM and two direction outputs per channel.
As I understand it, there are now 18 pin PIC's available with two PWM channels?.