The most attractive parts are in the north, where the mountains come right down to the water, but the lakeside roads can be very busy.
However the southern shore around Desenzano and Peschiera looked pretty uninspiring when I was there - very flat and lined with massive campsites for kilometer after kilometer.
Have you considered the other lakes? I liked Lake Como, which is also surrounded by high hills but not quite as hemmed in as Garda. I also particularly like Lake Iseo - quite a lot smaller but also less crowded than the big ones.