Besides the clockwise thing, I think most people start with Mexico because it has "Rio del Tiempo", and is close to Norway's "Maelstrom", the only 2 "rides" in WS (the rest being "attractions", and darn good ones, I might add!). I tend to skip Mexico (don't like it much), and love the rose walk, so I start with Canada. Besides, the crowds are lighter, and even if I end up walking into them at the end, I've had a nice, relatively crowd-free period in which to recoup my senses.
Never even noticed the sun thing...that's really good to know!