Just have your placard out if you're not driving a car with handicapped plates, and ask the guards politely.
It may have been because it was still the holidays or the new rules, but we were meeting family for dinner at the GF and we didn't have my hubbie's placard out (we don't drive with it hanging). We had to show it to the guard along with ID to prove we really were using valet like we asked, and even then we had to give the name of the reservation, even though it wasn't under our name.
The valet CMs had no issues.