Any outdoor places to play in San Fernando Valley/Burbank area? (No rinks that are on schedule)

I need to find an outdoor area that will allow me to put some rollerblades on and practice outdoors. My local park is strict and I can never play on the tennis courts. I need maybe a large area of cement or even a handball cement court.

Please don't reply with the Burbank or Noho roller rink, I am stricly looking for outdoor places to practice for free with no schedule.