Those times are conservative, but not inaccurate. You will be safe to leave that much time. On the bus from Poly to DTD, the actual ride takes about 15-20 minutes tops. But it can be slower if there is traffic, lift operation for scootetrs, or just poor luck. And they try to run the bus service loop with consitency, but somtetimes you can wait 30 minutes for the bus to show up (hence the 60 minutes time frame).
Driving -- if you are familiar with the route, shouldn't take more than 15 minutes.