Yeah, the salespeople who work in LA boutiques usually have really great style. And we have some pretty incredible boutiques.
But I think the best places to style watch are more under the radar, and that's why tourists might not get the chance to see some really great LA street style. First off, Robertson is a bit overrated. That includes Kitson. Fred Segal is overrun by tourists, but it's still considered hip. There's some good style watching to be done there, if you don't mind the occasional ten year old decked out in Chanel and LV or the over-botoxed mom in the tight True Religions(which, I guess, is an important, if not annoying, part of LA street style)
The best spots to style watch, in my opinion, are the hotspots. Geisha House, Blowfish, the Chateau Marmont Cafe, etc. (technically these aren't all in LA, but they all have the same Los Angeles-y vibe). You'll get to see the most stylish people in the city, as long as you don't mind the price.