Buses begin running at 6:30 am, be at the the bus stop by then and get the bus to MK, walk over to the resort monorail and take it to the Poly, which will be the third stop. Entire trip should take approx 45 to 60 min depending on how long you have to wait for the bus.
Mention to the bus driver where you are headed, sometimes they might just drop you right at the Poly, if they're not to busy or others on the bus are also going there.
The other alternative would be to take a taxi, and you could be there in 20 minutes from just about any Disney resort and a max fare of $20-$25. Bell services can arrange to get you the cab if there is not one already waiting outside your resort.