I also have the ET-73. My WSM is out on my patio, which is pretty big. The transmission distance for mine is limited in my experience but my bedroom is on the back of the house (brick), next to the patio. On overnights I just set the receiver on the window sill of the bedroom. Works great. If I put the receiver on my nightstand next to the bed the reception is sporadic at best. When not doing overnights, I set the receiver in a window of our laundry room (also on the back of the house, next to the patio). I can hear the alarms, but can't see the receiver, from the comforts of my Lazyboy. So, the cinder blocks may pose a problem for you.
As a side note, I think that setting the alarms for a temperature range, only taking action when the alarms go off rather than constantly monitoring the cooker temp by looking at the digital display, has made my finished products better. When I first got the ET-73 I carried it around with me and stressed over every degree change in temp of the cooker. I was constantly adjusting vents and "yoyoing" the temps. Now if I want to cook between 220 and 250 I set the low temp alarm for 200 and the high alarm for 270. Once dialed in the WSM usually settles around 240...without any further adjustments needed. So not being able to see the receiver has been a good thing, IMHO.