How often do you experience sexual attraction when out in public?

All the time. My partner and I often point out people we find attractive, we even rate them.
Because we have such a broad range(from young twinkies all the way to older bear types via androgyne and even feminine cis-women and rugged masculine types), there are always attractive people for us.
Plus we have a liking of beauty and attractiveness that doesn't fit into the "normal" conventions and ideals of what beauty and attractiveness means in our society.

Basically, a trip to Tesco is an hour long horn-fest.

 

Aesthetically, a lot. Sexually, never.