The number of people fishing may be a crowd of twenty on a Saturday afternoon in zone 1 or a stretch of water all to you on a Friday or Monday. A snowy day may find you all alone in the park with a few eagles perched on the Sycamore tree over the stream.
A mayfly hatch is common with a #20 BWO; imitating celery green body, a white tail and white legs Baetis emerging from the slough or back waters near the concrete access structures. I use a 4 wt 10 ft rod with 6X or smaller tippet. You will find me wading upstream looking for trout hunting these insects. Even if you never tried to fish a dry fly, these trout are blind to the many mistakes a fisherman starting out may make.
For more information of these mayflies check out: http://www.troutnut.com/hatch/180/Mayfly-Baetis-Blue-Winged-Olives