Most cars let you engage at 20mph going by my purchases since 2010. (Ford, Toyota, Kia all 20mph). The only weird one was my VW which let you engage at 25 then thumb it down to 20mph with the controls if I'm remembering correctly. I only know this because I'm a huge fan of this curvy 15 mile stretch of bayou road with a 20mph limit and its rare that a car hasn't let me engage it that low.
I can vouch for our Toyota letting me set it at lower speeds. Our city has a speed limit of 25 mph and there are long stretches of wide avenues where I’ll set it. Then I can spend more time looking out for kids darting across the street than worrying about speed control.
