I spent seven days going from Port Elizabeth to Cape Town via Addo a few months back. I don't regret the trip, but the Garden Route is pretty boring for large stretches, and if the road is blocked due to some township protest, then you could literally be sitting on the road for hours. The upshot is that I had a chance to drive through a major township in a convoy of other cars.

Although it was my first visit to South Africa and my experience there is limited, I would not recommend the Garden Route as a place to spend precious travel days. Sure, Addo is worthwhile, but you only need two days in and out of Port Elizabeth. Better to spend your other time exploring Cape Town and the Western Cape, or going to another reserve for a different experience.

If you do decide to drive the route, pick up a data SIM card and turn on google maps for directions. I found Vodacom to have pretty good reception along the main roads. Beware of the speed cameras though which google maps will not warn you about.

I stayed overnight at

Addo Elephant NP
Jeffreys Bay
Mossel Bay
Natures Valley
Oudtshoorn
De Hoop Nature Reserve

Outside of Cape Town, which is in a class by itself, my top three destinations along the drive were De Hoop, Addo and the area around Oudtshoorn (Swartberg Pass) followed by Nature's Valley. Jeffreys Bay might be interesting if you're into surfing and big waves, but otherwise is just a pit stop. Same sentiment for most of the other coastal towns such as Plett Bay and Knysna that people associate with the Garden Route.

Having said that, I found food to be excellent (with the exception of Plett Bay) and affordable throughout the journey and the people extremely friendly.

If you go to Addo, I can recommend the Aardvark Backpackers and the organic restaurant next door which was magnitudes better than the sole restaurant inside the main camp at Addo NP.

De Hoop has game too but it is probably more famous as a place to view the Southern Right whale or hike one of the coastal trails. Best to have a 4WD at De Hoop though as the roads are in terrible condition.