My town is still really underdeveloped and about 2/3rds of it is dedicated to hybrid plots, so I don't like to give people tours just because it's nothing special yet! Once it looks a little better, I might be more inclined to let people walk around, but I'd still follow them like a hawk and lay down all the rules just because I don't like what I've experienced from some people beforehand.
Whenever someone asks, I usually say something along the lines of, "My town is still pretty empty! There's not much to see. Haha!" And for some reason people take that as a cue to say, "Aw! I'm sure it's fine! I'm just going to run over here out of your sight now! Goodbye!" I've also had someone say, "Can I explore for a bit?" and then walk away (off the paths and over the places I'm trying to regrow grass) before I've ever answered...
Although in retrospect, I'm totally letting them wonder about my town since they never actually get to see it for themselves.