Driving to Quebec is easy, however once you enter the walled Old City, pedestrians rule so don't expect to move very fast.
In general, driving is not a problem. All the major rental car agencies are here. Just remember the signs are in French and the speed limits and distances are in kilometers.
From Montreal to Quebec City is an easy 3-hour drive right up either Canadian Highway 20 or Canadian Highway 40. 40 skirts the north edge of the St Lawrence River while 20 runs just to the south of the river. We chose highway 40 and stopped for a nice breakfast in the city of Trois Rivieres, at about the halfway point.
Some of you will rent cars in Québec province. First have to admit, Québec's driver may be slightly aggressive! Well they only want to get ahead of you, let them go they will be so surprise!
But, no joke, if you rent a car and drive from Montréal to Québec city do not use the # 20 highway ! Are you so in a hurry ? This road is so sad, a real punishment! Try instead the old road number 132, plan an entire day to go from one city to the other... you will see old traditionnal french canadian houses, small towns, great landscape and views on the Saint-Lawrence river. When coming back, are you more in a hurry? Now try the number 138 road, on the north shore of the river! Depending of the time of year, you will also see some fruits sellers along the road. Try their apple, strawberry, raspberry, etc. Try also their corn... we use to eat it directly from the stem of the fruit. adding some butter!
In Montréal, trust the Métro , it is the easiest way, reliable, safe and give you access to all the city!
To check how the traffic is going use this link with information on work and other problems.
Be careful with the public parkings owned by the SPAQ, those you have to put your credit card in when you go in and out when you go out. A computer bug happened and they kept charging my credit card. I had to make a few phone calls to correct this. The SPAQ was very professional and gave me back my money but I had a lot of trouble with my credit card company who nearly called me a liar and a thief.
I doubt it happens regularly, but do keep an eye on your credit card bills afterwards.
Here too we got by car and found a parking space near all sightseeings.
Parked our car and then we walked around. It is not a very big city so it is easy to walk around and see everything you want.