If you can get to the Ticket & Transportation Center, there is a RPDE van pick-up at the kennel. They do regular pick ups there.
I guess with Pop you can take the bus to the Magic Kingdom, then take the express monorail to the ticket & transportation center.
We've done both. If you have a rental car, you can go right to the track and they will let you take the car thru the tunnel to the office in the infield.