In my experience, the wait will be somewhere between 30 seconds and 2 hours. Sometimes a dust storm hits and stops traffic, sometimes the computer or phone or whatever goes down, sometimes everything flows smoothly.
Same thing with the drive in. Sometimes traffic goes fast, sometimes there is an accident on the 2 lane road and everything stops.
My advice is not to plan a specific time for anything. Make your plans flexible enough that you can find your friends and set up whenever you all happen to arrive.