well, i can't help you with central cali, but i was in frisco 4 years during college....
first off drive into downtown and park your car under union square... only one way in and out (on geary), so you can't really miss it. there are plenty of places to go and things to do within walking distance.
before doing anything, find one of the map dispensers on the street and grab a san francisco quide (free). the centerfold is a map of the downtown area with street directions (all one way). if you look at a map, you'll see all of these things are within 5-10 mins walk of union square:
on the northwest corner of powell and geary, is a bar called ponzu. i highly recommend this as a chill-out spot.
directly south of union square, on geary itself, is a macy's. on the top floor of macy's is a cheescake factory bar/restaurant. sit outside, on the deck... she'll love it. they don't take reservations though.
south on powell there is an awesome sidewalk pizza shop... if that's what the mood calls for.
three blocks south of union square (you should still be walking...) is market street. on market street is a massive 5 or 6 story shopping mall... if that doesn't earn you brownie points, nothing will.
on the northeast corner of powell and post, there is a fancy hotel (name forgotten). on the top floor of this hotel is the starlight lounge. great club, just make sure it's not 80's night or anything weird.
on the northeast corner of geary and mason (1 block west) is a club/bar called ruby skye... also very good.
from union square, head west on geary and then north on leavenworth. when you get to the northern shore you will be at ghirardhelli square. stop here for ghirardelli chocolate (i go with the shake) and enjoy it on the water. there is a restaurant here called gaylord (don't let the name phase you... it's not like that). incredible, though expensive, east indian food.
if you park near the intersection of jackson and broadway, walking north/south will take you to more very good restaurants. walking east/west will take you to a bunch of nice bars.
on embarcadero you have pier 31 and pier 39.... excellent clubs/bars, and daytime shopping. you can also catch the ferries out to the different islands (alcatraz, anyone?) from here...
DO NOT forget to stop by lombard and leavenworth (make sure you drive).... you'll understand when you get there.
i apologize for going on and on, but i'm talking about one of my favorite cities in the world... as if you couldn't tell.
p.s. keep your eyes focused on your girl... because there are some great "sights" to see in san francisco. have fun.
