I also pulled a HC permit for the prior week and although I haven't run the HC stretch, I've run the Lower Salmon too many times to count. Since the LS enters the Snake just below HC, I've taken out at Heller Bar often. Generally the jet boats are present but not obnoxious on the river. They are pretty respectful ... if you are. You will mostlikely see higher jet boat volume due to the 4th of July weekend which will only really be a problem at takeout, and maybe camping.
My suggestion, don't plan on using the HB ramp for anything besides the final loadout ... unstrap, organize, and prep your gear alongside the ramp on the gravel bar, bring your truck down at the last minute. As a second option, there is nice gravel bar upstream of Heller Bar, just below the confluence of that Grand Ronde has lots of unloading space, is quiet, near your the shuttle parking, but doesn't have a nice eddie. Also, if you have access to a motor (I know, goes against the grain), it's worth it on the 2day stretch below HC ... the water is pretty flat and the wind can be obnoxious. Personallly, I enjoy the row out but my BF rebelled and purchased a motor.
Feel free to shoot me any further questions.