JoJo,
Thanks for providing the park info. and map!!
mARTa,
Parking and Travel Town is free. Observatory itself is free ... if we drive up to Greek Theater and park there, which I believe is free parking, and then hike up for 5 mins ... it's free to visit the Observatory I believe. If you want to visit the LA Zoo and Museum, those you do need to pay ... can't remember how much, somewhere between 10 - 15 bucks I think ....
But don't need to worry about parking, you can park anywhere in the park for free, and parking is everywhere.