Don't wait for me to do what? I don't understand the sentence. You're saying "If you go to the bar, and don't see me there, then leave the bar (don't wait) and go somewhere else?"
Are you suggesting that the bar is a place to meet in preparation for going to another place?
If you go there and he doesn't arrive by 8 o'clock, don't wait any longer. If you go there and he hasn't arrived by 8 o'clock, don't wait any longer.
*If you go there and he didn't arrive by 8 ... *If you went there and he doesn't arrive by 8 ... *If you went there and he didn't arrive by 8 ... *If you go there and he hadn'