Fun things to do with my boyfriend?

I'm trying to figure out some fun things to do with my boyfriend but I'm fresh out of ideas. I live in Placentia CA which is kind of near Anaheim so I already know about Disneyland and Knott's but they are ridiculously expensive. Some ideas other than board games and picnics would be nice because we are a bit more adventerous (ie mountain biking, dirt biking, etc.) Not trying to be rude but I really don't need smart *** comments so if that's what you were thinking keep it to yourself please...thanks : )