Don't really know RenFaire ettiquitte, but I think you should only take your guitar if 1)You dress period, and 2)are willing to leave it in the car if it is not welcome (aarrrggh, not me!)
And, I got lost in the worst part of Dallas one night at 2AM, was a bunch of "homies" on the corner, so I just pulled over and asked them how to find Irving Blvd. (only it's boo-lay-vard in TexSpeak). They told me, and I was on my way! (Also managed to get lost in Lufkin the next day, Aine will get a kick outta that!)