Adventurous stuff
Antigravity chambers or Vertical Wind Tunnels
(I see you're also in Cali
, you might like them:
http://www.skydiveperris.com/ they offer both real and simulated/indoor skydiving). So much fun.
http://www.youtube.com/watch?v=eWDzrqtbwVw
Amusement parks (roller coasters, games, etc)
Helicopter tours
Surfing lessons
Shooting range
Rafting or Tubing
Certain race tracks offer "ride-alongs" where you get to experience speed racing with a professional driver.
Ideas for the more faint of heart
Shopping together at an open market or farmer's market and prepare a meal together with the fresh food you purchased
Summer block parties
Music or Film Festivals
Walking tour of a nearby city, or city-oriented scavenger hunt.
Aquariums or Planetariums
Salsa dancing
Car shows