Ok, hope I don't get flamed but. . . . . . in fact PLEASE don't I'm just voicing an opinion, and only doing what I was told I could do by a Disney employee.
When we had an early adr at Ohana's and we were planning on going to MK we used the Poly's valet service. It cost $7 but when tipping (my DH is a generous tipper) it ended up costing more than the $9 to park, but we did it for convenience. We didn't have to try to park, figure out the monorail's schedule and at the end of the day it was a godsend that the resort monorail's line was shorter than the one for the ttc and we didn't have to hunt our car down in a parking lot, or worry about trams, etc.
I did not feel bad because:
*we paid for it
*we were not taking up a parking space that is really for resort guests only, or those dining to use wihle they are dining only
*when we dropped off the car the valet told us we could leave the car there for as long as we wanted
In fact we did this at the grand floridian on the morning our son had his pirate cruise, we left it in valet when we went to MK afterwards, again the valet said to leave it as long as we wanted.