The other obvious choice is to take your car, if you have one.
Never stayed AT the Poly, but many other resorts. The wait time mid day (at every Disney resort) can be about 30 minutes for each bus. During peak times it is usually shorter, unless there is a crowd ahead of you and the bus fills up, and you have to wait for the next bus to arrive...but usually if the bus fills up, it's when you just got to the bus stop right when the bus was arriving.
So if you're looking at waiting 30 minutes for a bus then driving will be faster, except that when you get to the park, you'll still have to get through the pay booth (usually fairly short, but could be longer) , and also from the parking lot to the park entrance - which may take five minutes, or may take 15 depending on where you end up parking. So it won't really save that much time, esp. if you go during a peak time.