Or better yet, drive up Angeles Crest to Holcomb's Ranch. It's 20 miles of hairpin turns and a cool biker bar in the redwoods. It bike bar food (no one goes there for the food anyhow), but the drive is nice, and you'll have her all to youself in the mountain air. Just take it easy on the drinks since you have to drive all those turns back to town.
Another good one, is the LA Arboretum, but that's an all afternoon thing, and then you have to drive back to town to eat. It's only 20 minutes, but you're going to be really hungry when you get back. It's a nice 'hidden' treasure.
The Getty sounds good too, as drinks and the sunset are very nice.
If you like sushi, check out Yamashiro (sic), high up in the Hollywood Hills. Great view and good food.
Good luck!