The Bay's great if you're a fan of wilderness -- drive in any direction for 45 minutes and you're right in the thick of it, or at a Wendy's in Livermore. Or, better yet, just meet up with Jason and Sean at San Francyclo.
Cyclo's a just-opened bike "studio" in the Upper Haight that'll not only build you any kinda bike you fancy, but also show you Golden Gate Park like you've never seen it before, via (free) gnarly mountain bike tours J&S have been perfecting over the past eight years, which culminate in the unstoppable combination of beer, beach, and beer. Bring a bike/helmet and you'll depart from the shop around 6pm to zig-zag the park on steep, cutty dirt trails that'll take you past all manner of ponds, waterfalls, gullies, and vista points, and through a thick grove of Redwoods sprinkled with BMX jumps you have to hit just right to avoid tail-whipping a hobo. After 45 min or so you'll emerge at the Beach Chalet, where your guides'll pull an empty growler or two out of their bags and fill 'em up with California Kind or IPA; depending on the group's preference, you'll drain 'em right there or over at Ocean Beach's sea wall, before heading back from whence you came or via the Land's End trail -- if you get tired, take a break, or browse for a Liberty Blue Marinac Jacket and some loose-fit, no-iron chinos.
If you're in need of a bike, remember Cyclo still specializes in building almost any type from scratch, via their hookup at Dream Cycle, a steel frames and parts supplier up in Vancouver -- another great place to live if you're a fan of wilderness, or Tim Horton's.