Hi, mmm, what time of year are you coming? Oct-Nov is the best weather and visibility. Summer months tend to be foggy and colder. The 49ers often had better weather than the Giants did at Candlestick.
I second the suggestion to bicycle across the bridge. The bridge is pretty long. One problem about bicycling is that you’re on the west side of the bridge whereas the city and Alcatraz and Angel Island are east. So walk your bike on the east side of the bridge (if you can; please check the rules beforehand). And then for the return trip ride your bicycles back along the west side and you’ll get nice vistas of the hilly Marin (County) Headlands and the west side of San Francisco too.
Doing this gives you the best of both worlds, the east and west sides of the GGB with less time spent because you’ll ride the bike back.
If you do bicycle across, I highly recommend Battery Spencer on a clear day. Find it on the map, it offers stunning scenery from up high. My absolute favorite place.
If you walk across the GGB then take an Uber up to Battery Spencer. It’s my favorite place to take visitors. Last October I took this photo from there with my phone.
I’ve been going there since 1978!
Another unique-to-San Francisco activity is to take a San Francisco Love Tour. I did it once about 4 years ago and it was fantastic. https://sanfranciscolovetours.com/
Alcatraz is popular and it does sell out fast.
Hiking Angel Island is a great activity. You take in a lot of scenery on the island — SF, Berkeley, Oakland, Tiburon (where Robin Williams lived), and much of the north bay. I’ve been a few times and it’s great, and you take in more scenery on the boat ride to the island. I also did a Segway tour around the island and that was good too. Not sure if they’re still offered.
If you ride a cable car, I recommend riding the Powell & Hyde line. Not Powell & Mason, and not the California Street line. And get a round trip ticket. The view on the P&H going down Hyde St. is dramatic and much much better than any views on the other two lines. Catch the P&H from Market Street and take it all the way to the end. Take care because the P&M line also boards from the same place. Be sure to take P&H. When you’re in the line and you get to the front of the line, as the CC is boarding you’ll want to be the first to board the P&H CC. If you’re not the first to board then stay at the front of the line and as the CC is boarding let others behind you go ahead and board it. Tell them, and tell the SF MUNI workers that you want to catch the next P&H CC. Make up a story if you have to for the MUNI workers, like tell them you’ll be meeting someone at Ghirardelli Square and it’s a little to early to board the CC.
You’ll do this in order to be at the very front of the CC. Sit at the very front of the CC (or better yet if you’re the adventurous sort then stand on the side platform of the CC!), and also on its right side. Be sure it’s the right side because when it stops at Lombard St. you’ll get the best view of the crooked street and also a nice view of Coit Tower. Now when it stops at Lombard Street DO NOT get off there, not yet. Because right after the Lombard stop is the dramatic downhill and stunning vistas as you descend the hill on Hyde St. It’s this view that’s the reason for being at the very front. It is an amazing view.
A few years ago when I did a little Uber driving, even though I now live an hour south of SF, I liked to drive in SF, for (1) because I’m familiar with the streets and traffic there, but more importantly (2) because I liked to give tourists the ‘scenic’ way between where I picked them up and where they needed to go. If they had a little time I would explain what they’re seeing along the way. I liked being an ambassador of sorts for SF.
Twin Peaks — yes, recommended if visibility is good. Be sure to bring layers of clothing for possible cold wind. That goes for Battery Spencer too, or really any time you’re in SF.
Enjoy, mmm!