Perfect town in Animal Crossing Wild world?

I've done it, and it is tough. To do it as cheaply as possible:

First, make sure you have no weeds every day.

Buy flowers, and plant them in 2 by 2 squares. Water daily, and keep buying new flowers. As new flowers bloom and you buy them, keep making more 2 by 2 squares. Aim to get where you can always see one set or another of flowers; it doesn't hurt to have too many flowers, but you won't go perfect with too few.

Make sure you have plenty of trees, with no open holes. IE, make sure anywhere on screen you are, you can see a tree. Conversely, space out the trees so you can always clearly walk through them.

Finally, talk to the game characters daily. Especially Pelly, as she'll be able to tell you the status. Once Pelly says you're good, just keep things watered and weeded for two weeks.

To be clear: the 2 by 2 squares is just a personal thing; if you can afford more flowers go for it. I find that's just the easiest way to do this cheaply.