yay,
chloe, welcome to SF!!
I lived in the Bay Area for 11 years and loved it. I used to work downtown Financial District and in Mission Bay.
Embarcardero and Mission Bay have newer housing units and are newer areas with varying amounts of things to do in the after work and weekend hours.
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Embarcardero is fairly long and runs the length of the Bay waterfront, from AT&T Park to Fisherman's Wharf. There are high rise condo/apt. units along the way. I think it's kinda a sterile area, although there are some "neighborhoody" things coming in like supermarkets and restaurants. It's fairly busy during the day due to people working in the nearby SoMa and Financial District areas but at night seems a little deserted. AT&T Park is on one end and it's usually a zoo around there when the Giants are in town. Fisherrman's Wharf is awful
(IMO) - totally tacky stores and mediocre restaurants. Plus it's totally crowded in the summers. The whole stretch of Embarcadero has decent freeway access to 80 and 280 on the South end and fairly close to the GGB more toward Fisherman's wharf.
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Mission Bay is an "up and coming" area and used to be pretty sketch for a long stretch of 3rd Street. There's a ton of construction going on and some revitalization due to the influx of money for bio research (UCSF just built an enormous research campus there). I don't know how many of the housing units have been occupied yet. I just drove through there last week (avoiding rush hour traffic on 101) and while there are new buildings/lofts, etc. it doesn't seem as "neighborhoody" as other areas of SF. I would be a little worried at night too due to its sketchiness not-too-long-ago. Plus not too much to walk to. Good freeway access to 101 and 280.
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Lombard Street is pretty long and runs through several areas: North Beach and Cow Hollow/Marina - so for more details on neighborhood, do you have a cross street or area of Lombard where you're looking? It runs through popular neighborhoods and you can probably walk to lots of restaurants and stores and parks, depending on where you are on Lombard. Getting street parking is probably gonna suck, though. Gonna take you longer to drive through the city for freeway access to 101, 80 and 280. If you're in the Cow Hollow/Marina area, you're really close to the GGB. I'd probably go for this area if I were you.
Good luck! PM me if you have any questions.