How long are you staying over at US/IoA? I ask because a few years ago, my friend and I got a great rate at RPR...but we were both staying at BWV, each in our own studio. But, the room rate was so good (about $70 each), that we packed a backpack with clean undies, toiletries and such and took the Mears shuttle bus over for about $20 pp, r/t. We got to US/IoA by 7:45, got checked in at our resort and were at the front gates of IoA by 8:40...yeah, a bit behind the other resort guests, but still in front of the majority of the other guests. Then, the next day,we had early entry, stayed until about 4pm, got our shuttle back to BWV and continued our WDW stay. Yes, we had paid for our studios for a night we weren't in them...but it wasn't a big deal.
You can't take luggage on the Mears shuttle though...backpacks are fine, carryon bags are not. If you're going to be staying longer than one night, and then you may want to just get a cab or a car service.