When desiring to do street/documentary/urban I prefer to be alone, it's just less distracting and has less impact on potential human subject matter. Which is why I just couldn't see being involved in an urban "photo walk" with a group of photogs.
Landscape shooting is different, I don't mind others being with me, provided they don't mind waiting for me to compose and get the shot.
Depending who I'm with and the context, sometimes I know it's best to just not take photos, sometimes the social setting is more important than my own desires. This I've had to learn over the years.
~Joe