I started the 49 mile at The Embarcadero pier in a convertible. You can park and take beautiful pictures at this pier in the morning or evening when the lamps are all lit. You would follow a sign that looks like this:
You can download a map https://www.sftodo.com/maps/49-mile-scenic-drive-san-francisco.pdf. Also, I purchased a downloadable iPhone App for $3 - https://www.guidigo.com/Tour/United%20States/San%20Francisco/Drive-the-magic-that-is-San-Francisco/MgUHK6vwU-M?lg=en. It was well worth it. You can skip not so interesting spots and move on to the next, if you have little patience or little time.
The must do are to head over to the Cable Cars at Powell, Chinatown Gate, Transamerica Pyramid, Coit Tower, Lombard Street, Sea Lions on Pier 39, Ghirardelli Square, Golden Gate Bridge from Fort Mason, Palace of Fine Arts, Gate to Presidio, Twin Peaks. To cover all of these places, it may take a full day or two.
If you have a couple of more days, I would drive north to Nappa Valley and stay in one of the vineyards. My friend from the gym asked me about SF and a driving trip to LA. I suggested that she should do the above and drive down to Montery, Carmel & 17 mile drive south. Afterwards, they can take Highway 1 and head down to all the beaches to L.A.