Using the "16 x 16" patterns to each acre grid system from AC:WW, AC:CF seems to use a 5 x 5 grid. This means that the entire town is composed of 6,400 spaces, or spots for patterns. 80 patterns across and 80 patterns down. The bottom acre extends into the ocean.
This is what your town looks like in a grid:
You need between 12 and 16 trees with 4 flowers in each acre. Your results might vary but these numbers generally work. "Problem acres" may arise that require less trees, or trees moved around in the acre. You need to maintain a perfect town for 15 days to receive the golden watering can with the first day you are told that the town is perfect counted as Day 1.
Depending on who is on duty at the Town Hall, the following messages will be used when you have a perfect town:
Pelly: >"Fantastic! [TOWN NAME] is in great shape right now! Yep, its pretty sweeeeet!"
Phyllis:"Well, isn't living here better than you expected? (...Or maybe not.)"
Achieving perfect town status is also the only way to have Jacob's Ladders appear naturally in your town. One Jacob's Ladder may spawn each day that your town is in perfect status. Once you have perfect town status be sure to search your town each day for this rare flower.