What time does the parking area open? And can you walk from it to six flags or have to take their bus?

It is a good walk, no need for the bus. Parking should be good around 9am.

There are quite a few steps you have to go up and over the street. You can also use a ramp for strollers our those who can't do stairs.

The park opens most days at 10:30am. Get there early for the best parking. It is a short walk to the entrance.