recommendations
I personally don't have much experience with Carlsbad except for the area around the Outlet shops, which I would highly recommend. . . lots of high end stores.
I suggest multiple trips down to San Diego. Traffic is quite bad though during rush hour(s) though so either leave really early or wait until after 9 or 10.
San Diego has a plethora of activities, but let me share a recommendation for a romantic evening.
- Weeks prior to your visit, make a sunset reservation for the Prado restaurant in Balboa Park. Both the interior and patio are excellent, but I'd recommend the patio to experience Southern California's beautiful weather. My favorite dishes: the Osso Buco and the Pork Prime Rib. If you really like this restarant, then check out the other restaurants owned by the Cohn family. Every one that I've been to has offered generous portions of gourmet fare at reasonable prices. Plus, service is normally excellent.
http://cohnrestaurants.com/cohn/pradobalboa/
- Arrive at Balboa Park at least an hour prior to your reservation time. This will allow you to wander through the many Balboa Park museum buildings. You might wish to check out this website and see if there are any museums that you'd like to visit in the afternoon. Just don't squeeze in the nearby SD Zoo on your date night.
http://www.balboapark.org/index.htm
- After dinner, discover how beautiful Balboa Park is at night. Then drive 1 mile to Karen Krasne's Extraordinary Desserts on Fifth Avenue. Zagat Guide had previously rated this upscale dessert experience as the highest rated eatery of any kind in the San Diego area. I personally love the home made ice creams and have bought the flawless cakes as gifts. The line to order can get long with the theater crowd, but I have rarely had to wait for a table.
http://extraordinarydesserts.com/extraordinarydesserts/
If all goes as planned, this itinerary will probably be the best experience of your trip. Another night, make sure to spend at least 2 hours walking around the Gaslamp District.