Yes! WDW guests who have a valid handicapped parking permit/tags do receive complimentary valet parking at the resorts. Personally we tip both when we leave the car & again when we pick it up.
I agree with JudithM on the tipping; I tip both in and out, usually $2.00 each way. However, if the valet assists with the ECV (disassembling and putting in the trunk, or removing from trunk and assembling) I will tip $5.00.
Note that the valets are tip positions, and the tips have gone down a lot since Disney started charging for valet parking; it says right on the ticket that none of the payment goes to the valets.