You asked for scooter or bike recommendations, but I love the Boosted Board electric skateboards for their portability and fun factor. However, they're almost

You asked for scooter or bike recommendations, but I love the Boosted Board electric skateboards for their portability and fun factor. However, they're almost certainly more dangerous, and a higher learning curve (though I hadn't skateboarded much before getting one). Just watch out for Muni tracks, gravel, wet roads (especially on metal), and potholes.