If you are in a wheelchair, I expect attendants will help you into the motor boat that goes between the resorts and CityWalk. I don't know about ECVs; they might be a bit too heavy to lift in and out of the boat.
The Hard Rock is VERY close to the parks and should be a breeze in an ECV. Even Portofino isn't that far.I
Author of "Universal Studios Escape: The Ultimate Guide to the Ultimate Theme Park Adventure"ÃÂ