I bought a used P-18 last spring. This summer my spouse and I spent 4 days on Lake Michigan's Grand Traverse Bay, all 4 nights on the boat. Later, we spent 9 days on the boat in Lake Huron's North Channel.
To me, the P-18 is a primo trailered pocket cruiser. What mostly distinguishes this from other 17 to 19 footers is the open and relatively roomy interior (no mast support post or bulkheads), and the ballasted shoal draft keel w/ fiberglass centerboard. For two people, its spartan living, but quite doable. Best of all she sails great, looks good and has a comfortable cockpit.
We keep her on a trailer, daysailing occasionally on a local inland lake.
Absolutely no regrets with this purchase. She's a sweetheart.