What is a "dilute" solution of HCl?

Usually, dilute HCl for cleaning is around 2-3M. As for pH adjusting, it depends on what you have to adjust. I had to adjust HPLC mobile phase with 0.005M HCl, because the buffer component was quite weak (KH2PO3, in fact). But other times, I had to use 1M, because the buffer component was stronger.