There is at least one designated handicap spot in the lot (may one or two more). No guarantee, I am sure that one would be available and the lot, though convenient does fill up and they depend on that overflow lot.
Also, not all rooms are handicap accessible.
I did not see designated handicap parking. The parking in the hotel lot is all right underneath the rooms of the hotel, so distance wouldn't be a problem. Those spaces are limited and the overflow lot is 3 blocks away. This is probably the bigger issue.
Get an answer from Hotel Ruby staff and past guests.