State Parks in California you cannot climb trees as a private citizen just visiting the park. I would say though its less frowned upon on BLM or Forest Service land for sure. I think too at Municipal parks as long as your do lower hanging practice and just messing around with your ropework...
Next Time I am back at my parents place in CT, There's a huge tulip, that needs to be climbed. Its girth can rival the avg redwood out here. Although its 1/2 as tall. I miss nice big open branch structures of deciduous tree back east, so nice for fun climbing and easy to get into.
Price from USPS website
Priority Mail
Small Flat Rate Box $5.95 $5.25
8-5/8" x 5-3/8" x 1-5/8" Inside
8-11/16" x 5-7/16" x 1-3/4" Outside
http://pe.usps.com/text/dmm300/Notice123.htm#2454091