Everyone knows the Top of the Mark for great views, smooth jazz, and overpriced cocktails. But this, the granddaddy of San Francisco hotel bars (which famously refused service to Charles Mingus because he was black), is the perfect place for a single lass to make the acquaintance of an older (read: loaded) gentleman. The bands, usually a parade of slick R&B acts with their fingers on the "Proud Mary" trigger, are well versed in mid-tempo soul numbers that won't irritate his arthritic hip, with just enough strut to keep the crowd lookin' for love. A word of caution to greenhorn gold diggers: Have fun scoring free drinks, but as is true with all hotel bars, a lot more trouble is little more than an elevator ride away.