Yes, in dual mono mode, a mono signal is sent to all speakers regardless of connection to an L or R terminal.

Thanks Superstar. Outside of the dual mono feature, I was concerned with if the amp would function properly with the imbalance of one speaker in the right channel and two speakers wired in parallel on the left channel. 

I have a single mono outdoor speaker connected to just the left channel and nothing connected to the right channel of the Amp. The Amp is in dual mono mode with the EQ balance setting set all the way to the left “+20L”. My speaker sounds great and my Amp is functioning flawlessly.