They are in the same room, but the single riders are in the top section. There is a railing between the top and bottom section. There is a castmember stationed at the top section, so, they would see you jump down to the standby line.
Yep and in order to drop down to the next section, you would need to be light on your feet. Plus, going in the single rider line at Rock N Roller Coaster in order to beat the stand by line isn't all that great as the single riders' line is let into the preshow area only once for every two times of the other lines. And it could even be longer depending on how many single riders are waiting at the end of that preshow area.