Suttle suggests parking where you indicate here. But if that gate is open (like Matthew and I found it) I would suggest driving that last mile. The road is decent for passenger cars and the hike isn't that great with the radio stations positioned every hundred yards along the way.
I was thinking of driving up but I decided not to as this might have a negative impact on our "prescriptive easement". I never want to do something that could hinder our groups access in the future (learned that one from mountain biking years ago). Heck i need the exercise anyway :-)
You can drive up if you want to. If you come up from the other direction (Gates Canyon) there is no gate at all. There are no clear markings of where Gates Canyon ends and Blue Ridge begins. The road does get a little rough in places, as erosion takes it's toll. I have a small passenger car, not in the best condition, so I drive slow and avoid the larger ruts.