Huntington Gardens (http://www.huntington.org/webassets/templates/general.aspx?id=17082) is an enormous botanical gardens, conservatory, and library in San Marino (south of Pasadena). Right now it's around time for a lot of species to have their early summer bloom, so it should be a fantastic time to go.
The grounds are huge, 120 acres, so this also qualifies as a mild hike.
Let's meet around 11 at the entrance, and head in together around 11:30. We'll eat lunch in the cafe inside the grounds.
Admission is $25. No advance tickets needed. Parking is plentiful and free.
Note: I've scheduled this Meetup in conjuction with the Introverts of LA group.