There is parking all along the front where the Dhow's are, or when you get to the roundabout at the end the creek run where the Rulers COurt is there is a car park there, alternatively follow that road around to the left and up and then right down to the museum and there are a few car parks in that area too... lots of stuff for kids going on down there today if you them...
Just got back from the Creek.... as Moscow said hit the 66 down pass WAFI on your right and thru Oud Metha and then take the 79 for Bur Dubai you will see brownish signs for the Bastakiya area..... Lovely down there this morning..
Not sure if there's a faster way, but 2 alternatives I would try from the Ranches are...
Go down Al Ain Rd then down to Trade Centre Roundabout and turn Right onto trade Centre Rd, keep going and eventually you'll come to the Creek, (after the Burjuman) go left (I think you have to go right, then a u turn) and that road leads you to the roundabout at the bottom of Bastakiya.
Alternatively, go down Al ain Rd, but carry straight on down Oud Metha Rd. St on at the junction by Makhtoum Bridge, then right at the first junction, then left and again you are by the Creek on the road that leads to the Bastakia roundabout.