Casual Dress B-day Dinner
sushi for 100 bucks is super super difficult, unless you restrain yourself... you might try sushi ike in hollywood though.
you might also consider going to vibrato jazz and grill up at the top of beverly glen and mulholland for dinner and jazz. (not really between pasadena and orange county per se, but it's an evening all in one)
you could share plates at Lou, a great wine place
you might if you order carefully be able to work at Enoteca Drago (but bring your own wine)
in pasadena, whynot hit up Bodega Wine bar
tapas at cobras and matadors or at minibar on cahuenga or at tasca
I'm thinking somewhere in between Pasadena and Orange County. If your boyfriend loves seafood, then by all means, stick to that. Here are a few suggestions:
1. Admiral Risty - 31250 Palos Verdes Drive - classic seafood simply prepared
2. Buggy Whip - 7420 La Tiijera Blvd. - Very old school. Surf and turf. I go strictly for the giant stone crab claws. If you love them as much as I do, call first to make sure they have them.
3. Enterprise Fish Company - 174 Kinney Street in Santa Monica - mesquite grilled seafood
4. Gulfstream - 10250 Santa Monica Blvd. (Century City Shopping Mall) - I love this place. Good seafood, not great, but very good. Part of the Houston's family. Very professional service in a nice atmosphere.
5. Kincaid's - 500 Fisherman's Wharf on the Redondo Beach Pier - surf and turf - great ocean view - would make a nice birthday gift.
$100 with a bottle of wine might be a little ambitious, but depending on your appetites and some careful picking of the wine it may be doable. This place is French / Moroccan food and is not only inventive in its food, quite delicious but it's also quiet and casual.