When you come to explore Quebec City.....it is imperative that you bring good footwear along with you...
To really see and experience Old Quebec City I think the best way to see the most if its possible is by WALKING......
In my opinion to rent a car is a total waste of money....for the odd thing you might want to see or do that would require a vehicle there are tours available that you can use that are reasonably priced.
When you get to Quebec, plan just to leave your car and walk everywhere. This is a really safe city where everybody is out walking around even in winter. What I liked about this city is everybody was walking or biking around even if it was snowing and cold. These are narrow streets so driving is a pain, plus you want to hit the bars and enjoy the nightlife. Walk around and view the whole city from your own two feet!
You definitely do not need a car to get around Quebec City, the Upper and Lower towns of Old Quebec were compact enough to see on foot, they look much bigger on the map than they really are. We also walked to the Citadel and the Plains of Abraham and along the Grande Allee outside the city walls.
If you do drive to Quebec City, park the car and leave it there until you're ready to go.
Quebec is a very walkable city, although I wouldn't recommend anyone duplicating all the walking we did in one day!
We started from Chateau Frontenac and walked up St. Anne to Des Jardins and back down Buade. The large, silver-roofed building on our right was a university, we discovered - not open to tourists, but nice to look at. We worked our way counter-clockwise around the walls, then dipped down outside the walls to the Old Port Market and the Chateau-esque train station. Back inside the walls, we walked through Artillery Park and out Port St. Jean, one of the remaining historic gates in the wall.
Welcome to the modern world! We went to the Hilton Quebec on Rene Levesque (on the advice on a VT member, looking for a great view of the city,) but weren't able to get to any windows on the top floor.
Next it was around the traffic circle by Parliament to the Plains of Abraham west of the Citadel. We skipped the Citadel tour, but wandered around its outer ramparts and back down to the Chateau. Whew!
Your main mode of transport around le Vieux Quebec is YOUR LEGS. That's right. Get ready to trek. And we're not talking flat streets here, people. Be forewarned, those with plantar fascitis, Morton's neuromas, peroneus longus tendonitis, the infamous "bad knees", and anything else that may hinder you. HOWEVER, I must say that if you are willing to pay, you can play. So don't let any degree of disability scare you off.