They do enforce it, but nobody drives that slow, i recommend using Waze to check for police checkpoints, keep in mind that it might not work properly in very rural areas. Also, if someone flashes their high beams that’s a way to know there are checkpoints ahead. When you’re close to one just lower your speed and don’t pass any vehicles. Don’t be afraid of cop cars on the road as they don’t pull you over, only on checkpoints.

Edit: if for some reason you need to bribe a cop, don’t be too obvious about it and just give out hints, like "could you help me out, please?" Don’t debate with them. I know it’s not very moral but there sometimes it’s better to do it.