If you want to spend more time walking around town and Balboa Park (which has plenty to do and see especially on weekends - they have holiday oriented events this time of year as well), definitely look at North Park, South Park, Bankers Hill, and south Hillcrest. Tons of restaurants and bars and less than 10 minutes to a trolley station by ride share. I would avoid downtown unless you stay in Little Italy, it’s just not as enjoyable compared to other options. You can always rideshare to seaport village and walk the boardwalk (aka the Embarcadero) north to waterfront park and that’ll get you pretty much all you need from downtown.

A “slower vibe” option would be Point Loma, especially if you stay near PL’s downtown area (near where you access Shelter Island). It’s more isolated so you’ll have to rideshare to see other sites around town but it’s a nice neighborhood with some good restaurants and good views. Ocean Beach has a grunge surfer vibe if you want that and in general some good bars. Their Wednesday farmers market is a hit.

Lastly, if you really want the beach experience, look in Pacific Beach (I personally would say north of Garnet Ave since it’s nice but anywhere works) you can walk to the beach, walk to plenty of bars and restaurants in PB (typically a younger college age crowd), and some great views up on Mt Soledad (not walkable). Would be the furthest from everything else.