If you get a 3-day pass, try to make sure it includes cable car rides. They're so great!!
i live in SF and highly recommend walking in SF in June - if you can't walk up hills, just walk on flat streets or in areas with limited inclines:

ferry building / embarcadero (like a Quays) / fisherman's wharf - nice waterfront views
the mission / noe valley - mix of old-school San Francisco and gentrification
hayes valley
The marina (Union / chestnut street) - every city has their Rodeo Drives

no matter how young and strong you are, I suggest you avoid Civic Center, the Tenderloin, and Soma. Amidst the billion-dollar business hqs are a lot of unstable people and structures.