Really depends on the course. We've got a course where we are easily 30-34mph through it because it's on the end of a downhill. Speeds really should just be slightly less than whatever speed you are carrying through the straight, all things being right. So if you are pulling 25 through the straights, 23-25 through the corners at the front.

There shouldn't be much of a slowdown to turn in a 4 corner city crit.