In my gated subdivision (private roads etc.) it clearly states in the CCRs (Deed Restrictions) that the speed limit is 25 MPH. Local law also states that police, sheriff, constables, etc do not patrol on private property like ours UNLESS the offense is egregious. That rules them out.
Since speeding is a violation of the CCRs, just like not mowing your grass or painting your front door pink, it can be enforced like any other deed violation. We are not under the "State's Radar Gun Operators'" code so, for all pratical purposes, my 10 year old can shoot radar and issue a DEED VIOLATION. NOT a ticket to be paid in court.
It doesn't take a professional landscaper to see if a yard needs mowing to declare it in violation nor do we need professional painters to determine if a front door is indeed pink. Likewise, we don't need a certified trained radar gun expert to shoot rader. In fact, our CCRs state that the POA will enforce CCRs via "it's agents".
Little green men, bicycles in the road, calling the cops? Really? I don't want my subdivision looking like Fred Sanford's junk yard.
Read the CCRs. I'll bet you have more control then you think.