What cities in the state have the biggest interchanges and most road signs? (i.e., Lexington, Louisville, etc.)
Biggest interchange I know of is the I-71/75 and I-275 stack in northern Kentucky. I-275 and I-471 is another one. If you can stand to navigate the construction, there's Spaghetti Junction in downtown Louisville.
Just drove through SJ tonight - if you don't hit at rush hour, it's not bad at all. Just watch your speed in the "No Fly Zone" on the Indiana side.
You can see some dual metric/Imperial signs in I-265 in Louisville's East End.
In terms of sign quantity, stick to the Kentucky suburbs of Cincinnati.