I agree with TheFrog. Cat 22 would be the perfect choice for you. There are plenty of nice daysailors out there in your price range. Have a look on yachtworld. Also take a look at Precision 21 & 23, Hunter 21, Seaward, and COmPac to name a few. My ComPac 23 has a keel, but only draws 2' 3" of water. You could trailer it, but a centerboard design would be better for trailer sailing. Smaller options include cat 18, precision 18, west wight potter 19, and sanibel 18.
ANother interesting boat, which would be great for daysailing in protected waters is the Sea Pearl 21. Very easy to setup, minimal draft, cat ketch rig. Overnighting is more like camping though, and the boat isn't made for rough water.