There are a number of "landowners" here:  UCSC, State Parks (both Wilder and HCRSP).  If you can point somewhere online where this "implicit permission" exists in publicly-accessible clarity (from State Parks and/or UCSC), then access=permissive might very well be correct.

For example, I got a letter from AASHTO (national-level route numbering protocol authority) to number bicycle routes that I enter (and posted a link to this letter in our wiki).  For another example, I have direct emails from the Watershed Manager of the City of Santa Cruz to tag watershed lands (around Loch Lomond) exactly as they are presently tagged.

Absent those, the more restrictive tagging (access=no) applies, as that is the best data I'm working with.  For access=permissive, all we need is an agency (or ranger...something authoritative) that says "it's OK to ride here, but we reserve the right to restrict this in the future..." and I'm fine with access=permissive.  But (in this case, as it has been so contentious) OSM really needs something more than simply one mapper's word — we need some documentation as to the actuality of the permissiveness.  Thanks for understanding we have a relatively high burden of "proof" here.